Water-dispersible, cationic polymers, a method of making same and items using same

ABSTRACT

The present invention is directed to triggerable, water-dispersible cationic polymers. The present invention is also directed to a method of making triggerable, water-dispersible cationic polymers and their applicability as binder compositions. The present invention is further directed to fiber-containing fabrics and webs comprising triggerable, water-dispersible binder compositions and their applicability in water-dispersible personal care products, such as wet wipes.

FIELD OF THE INVENTION

The present invention is directed to ion-sensitive or triggerable,water-dispersible or water-soluble cationic polymers and polymerformulations. The present invention is also directed to a method ofmaking ion-sensitive or triggerable, water-dispersible or water-solublecationic polymers and polymer formulations and their applicability asbinder compositions for disposable items. The present invention isfurther directed to disposable items, such as wet-wipes comprisingion-sensitive or triggerable, water-dispersible binder compositionsincluding cationic polymer or polymer formulations.

BACKGROUND OF THE INVENTION

For many years, the problem of disposability has plagued industrieswhich provide disposable items, such as, diapers, wet wipes, incontinentgarments and feminine care products. While much headway has been made inaddressing this problem, one of the weak links has been the inability tocreate an economical coherent fibrous web, which will readily dissolveor disintegrate in water, but still have sufficient in-use strength.See, for example, U.K. patent disclosure 2,241,373 and U.S. Pat. No.4,186,233. Without such a product, the ability of the user to dispose ofthe product by flushing it down the toilet is greatly reduced, if noteliminated. Furthermore, the ability of the product to disintegrate in alandfill is quite limited because a large portion of the productcomponents, which may well be biodegradable or photodegradable, areencapsulated in or bound together by plastic which degrades over a longperiod of time, if at all. Accordingly, if the plastic disintegrated inthe presence of water, the internal components could degrade as a resultof the rupture of the plastic encapsulation or binding.

Disposable products, such as diapers, feminine care products and adultincontinent care products may be made to be disposed by flushing downtoilets. Usually such products comprise a body side liner which mustrapidly pass fluids, such as urine or menses, so that the fluid may beabsorbed by an absorbent core of the product. Typically, the body sideliner may be a coherent fibrous web, which desirably possesses a numberof characteristics, such as softness and flexibility. The fibrous web ofthe body side liner material may be typically formed by wet or dry (air)laying a generally random plurality of fibers and joining them togetherto form a coherent web with a binder compositions. Past bindercompositions have preformed this function well. However, fibrous webscomprising these compositions tended to be non-dispersible and presentproblems in typical household sanitation systems.

Recent binder compositions have been developed which can be moredispersible and are more environmentally responsible than past bindercompositions. One class of binder compositions includes polymericmaterials having inverse solubility in water. These binder compositionsare insoluble in warm water, but are soluble in cold water, such asfound in a toilet. It is well known that a number of polymers exhibitcloud points or inverse solubility properties in aqueous media. Thesepolymers have been cited in several publications for variousapplications, including (1) as evaporation retarders (JP 6207162); (2)as temperature sensitive compositions, which are useful as temperatureindicators due to a sharp color change associated with a correspondingtemperature change (JP 6192527); (3) as heat sensitive materials thatare opaque at a specific temperature and become transparent when cooledto below the specific temperature (JP 51003248 and JP 81035703); (4) aswound dressings with good absorbing characteristics and easy removal (JP6233809); and (5) as materials in flushable personal care products (U.S.Pat. No. 5,509,913, issued to Richard S. Yeo on Apr. 23, 1996 andassigned to Kimberly-Clark Corporation).

Other recent binders of interest include a class of binders, which areion-sensitive. Several U.S. and European patents assigned to LionCorporation of Tokyo, Japan, disclose ion-sensitive polymers comprisingacrylic acid and alkyl or aryl acrylates. See U.S. Pat. Nos. 5,312,883,5,317,063 and 5,384,189, the disclosures of which are incorporatedherein by reference, as well as, European Pat. No. 608460A1. In U.S.Pat. No. 5,312,883, terpolymers are disclosed as suitable binders forflushable nonwoven webs. The disclosed acrylic acid-based terpolymers,which comprise partially neutralized acrylic acid, butyl acrylate and2-ethylhexyl acrylate, are suitable binders for use in flushablenonwoven webs in some parts of the world. However, because of thepresence of a small amount of sodium acrylate in the partiallyneutralized terpolymer, these binders fail to disperse in watercontaining more than about 15 ppm Ca²⁺ and/or Mg²⁺. When placed in watercontaining more than about 15 ppm Ca²⁺ and/or Mg²⁺ ions, nonwoven websusing the above-described binders maintain a tensile strength greaterthan 30 g/in, which negatively affects the “dispersibility” of the web.The proposed mechanism for the failure is that each calcium ion bindswith two carboxylate groups either intramolecularly or intermolecularly.Intramolecular association causes the polymer chain to coil up, whicheventually leads to polymer precipitation. Intermolecular associationyields crosslinking. Whether intramolecular or intermolecularassociations are taking place, the terpolymer is not soluble in watercontaining more than about 15 ppm Ca²⁺ and/or Mg²⁺. Due to the stronginteraction between calcium ions and the carboxylate groups of theterpolymer, dissociation of the complex is highly unlikely because thisassociation is irreversible. Therefore, the above-described polymer thathas been exposed to a high Ca²⁺ and/or Mg²⁺ concentration solution willnot disperse in water even if the calcium concentration decreases. Thislimits the application of the polymer as a flushable binder materialbecause most areas across the U.S. have hard water, which contains morethan 15 ppm Ca ²⁺ and/or Mg²⁺.

In a co-pending application assigned to Kimberly Clark; i.e., U.S.patent application Ser. No. 09/223,999, filed Dec. 31, 1998, thedisclosure of which is incorporated herein by reference, there isdisclosed a modification of the acrylic acid terpolymers of theabove-referenced patents to Lion Corporation. Specifically, U.S. patentapplication Ser. No. 09/223,999 discloses a sulfonate anion modifiedacrylic acid terpolymers which has improved dispersibility in relativelyhard water; e.g., up to 200 ppm Ca²⁺ and/or Mg²⁺, compared to theunmodified Lion polymers. The wetted sheet is flexible and soft.However, the Lion Corporation ion-sensitive polymers of theabove-referenced patents and the sulfonate anion modified acrylic acidterpolymers of the co-pending application, when used as binders forpersonal care products, such as wet wipes, typically have reducedinitial sheet wettability, increased dry sheet stiffness, increasedsheet stickiness, reduced binder sprayability and relatively highproduct cost.

Another approach to dispersible personal care products is disclosed inU.S. Pat. No. 5,281,306 to Kao Corporation of Tokyo, Japan. This patentdiscloses a water-disintegratable cleansing sheet; i.e., wet wipe,comprising water-dispersible fibers treated with a water-soluble binderhaving a carboxyl group. The cleansing sheet is treated with a cleansingagent containing 5%-95% of a water-compatible organic solvent, a saltand 95%-5% water. A preferred organic solvent is propylene glycol. Thecleansing sheet retains wet strength and does not disperse in theorganic solvent-based cleansing agent, but disperses in water. However,because of the high viscosity of carboxymethylcellulose, which makes itdifficult to apply to fibrous webs, the presence of an organic solvent,and the sensitivity to hard water, the composition of this patent haslittle commercial applicability.

Although many patents disclose various ion and temperature sensitivecompositions for water-dispersible or flushable materials, there existsa need for dispersible products possessing softness, flexibility, threedimensionality, and resiliency; wicking and structural integrity in thepresence of body fluids (including feces) at body temperature; and truefiber dispersion after toilet flushing so that product does not becomeentangled with tree roots or at bends in sewer pipes. Moreover, there isa need in the art for flushable products having water-dispersibility inall areas of the world, including soft and hard water areas.Furthermore, there is a need for water-dispersible binders that do notreduce wettability of product with which they are used and are sprayablefor relatively easy and uniform application to and penetration intoproducts. Finally, there is a need for water-dispersible, flushable wetwipes that are stable during storage and retain a desired level of wetstrength during use and are wetted with a wetting composition that isrelatively free, or is substantially free, of organic solvents. Such aproduct is needed at a reasonable cost without compromising productsafety and environmental concerns, something that past products havefailed to do.

SUMMARY OF THE INVENTION

The present invention is directed to ion-sensitive cationic polymers andpolymer formulations and to triggerable cationic polymers and polymerformulations, which have been developed to address the above-describedproblems associated with currently available, ion-sensitive polymers andother polymers described in literature. The ion-sensitive polymerformulations of the present invention have a “trigger property,” suchthat the polymers are insoluble in a wetting composition comprising aninsolublizing agent of a particular type and concentration, such asmonovalent salt solutions at concentrations above about 2%, but aresoluble when diluted with water including hard water with up to 200 ppm(parts per million) calcium and magnesium ions. Unlike someion-sensitive polymer formulations, which lose dispersibility in hardwater because of ion cross-linking by calcium ions, the ion-sensitivecationic polymer formulations of the present invention are insensitiveto calcium and/or magnesium ions at concentrations of a few hundred ppmand are insensitive to pH variations. The ion specific cationic polymersand polymer formulations of the present invention have a “triggerproperty,” such that the polymers are insoluble in a wetting compositioncomprising an insolublizing agent of a particular type andconcentration, such as a divalent metal salt capable of forming complexanion in solution at concentrations above about 0.5%, but are solublewhen diluted with water including other ions, such as divalent saltsolutions as found in hard water with up to 200 ppm (parts per million)calcium and magnesium ions. Consequently, flushable products containingthe polymer formulations of the present invention maintaindispersibility in hard water or soft water.

The polymer formulations of the present invention are useful as bindersand structural components for air-laid and wet-laid nonwoven fabrics forapplications, such as body-side liners, fluid distribution materials,fluid intake materials (surge) or cover stock in various personal careproducts. The polymer formulations of the present invention areparticularly useful as a binder material for flushable personal careproducts, particularly wet wipes for personal use, such as cleaning ortreating skin, make-up removal, nail polish removal, medical care, andalso wipes for use in hard surface cleaning, automotive care, includingwipes comprising cleaning agents, disinfectants, and the like. Theflushable products maintain integrity or wet strength during storage anduse, and break apart or disperse after disposal in the toilet when thesalt or ion concentration falls below a critical level. Suitablesubstrates for treatment include tissue, such as creped or uncrepedtissue, coform products, hydroentangled webs, airlaid mats, fluff pulp,nonwoven webs, and composites thereof. Methods for producing uncrepedtissues and molded three-dimensional tissue webs of use in the presentinvention can be found in commonly owned U.S. patent application, Ser.No. 08/912,906, “Wet Resilient Webs and Disposable Articles MadeTherewith,” by F.-J. Chen et al., filed Aug. 15, 1997; U.S. Pat. No.5,429,686, issued to Chiu et al. on Jul. 4, 1995; U.S. Pat. No.5,399,412, issued to S. J. Sudall and S. A. Engel on Mar. 21, 1995; U.S.Pat. No. 5,672,248, issued to Wendt et al. on Sep. 30, 1997; and U.S.Pat. No. 5,607,551, issued to Farrington et al. on Mar. 4, 1997; all ofwhich are incorporated herein by reference in their entirety. The moldedtissue structures of the above patents can be especially helpful inproviding good cleaning in a wet wipe. Good cleaning can also bepromoted by providing a degree of texture in other substrates as well byembossing, molding, wetting and through-air drying on a textured fabric,and the like. The cationic polymers and polymer formulations of thepresent invention are particularly useful as a binder for fibrousmaterials because the polymers and polymer formulations are substantiveto the fibers.

Airlaid material can be formed by metering an airflow containing thefibers and other optional materials, in substantially dry condition,onto a typically horizontally moving wire forming screen. Suitablesystems and apparatus for air-laying mixtures of fibers andthermoplastic material are disclosed in, for example, U.S. Pat. No.4,157,724 (Persson), issued Jun. 12, 1979, and reissued Dec. 25, 1984 asRe. U.S. Pat. No. 31,775; U.S. Pat. No. 4,278,113 (Persson), issued Jul.14, 1981; U.S. Pat. No. 4,264,289 (Day), issued Apr. 28, 1981; U.S. Pat.No. 4,352,649 (Jacobsen et al.), issued Oct. 5, 1982; U.S. Pat. No.4,353,687 (Hosler, et al.), issued Oct. 12, 1982; U.S. Pat. No.4,494,278 (Kroyer, et al.), issued Jan. 22, 1985; U.S. Pat. No.4,627,806 (Johnson), issued Dec. 9, 1986; U.S. Pat. No. 4,650,409(Nistri, et al.), issued Mar. 17, 1987; and U.S. Pat. No. 4,724,980(Farley), issued Feb. 16, 1988; and U.S. Pat. No. 4,640,810 (Laursen etal.), issued Feb. 3, 1987, the disclosures of which are all incorporatedherein by reference.

The present invention also discloses how to make water-dispersiblenonwovens, including cover stock (liner), intake (surge) materials andwet wipes, which are stable in fluids having a first ionic composition,such as monovalent ions or divalent metal complex anions at a particularconcentration substantially greater than is found in typical hard wateror soft water, using the above-described unique polymer formulations asbinder compositions. The resultant nonwovens are flushable andwater-dispersible due to the tailored ion sensitivity, which can betriggered regardless of the hardness of water found in toiletsthroughout the United States and the world.

The present invention further discloses an improved wetting compositionfor wet wipes. Wet wipes employing the polymer formulations of thepresent invention are stable during storage and retain a desired levelof wet strength during use and are wetted with a wetting composition orcleaning agent that can be relatively free, or is substantially free, oforganic solvents.

These and other objects, features and advantages of the presentinvention will become apparent after a review of the following detaileddescription of the disclosed embodiments and the appended claims.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

The present invention can be practiced using two different triggerablecationic polymers or polymer compositions. One triggerable, cationicpolymer composition is an ion-sensitive cationic polymer composition andthe other is an ion-specific cationic polymer and polymer composition.These two systems will be discussed further below. Each of thesecationic polymer compositions may also optionally include a co-binder,which may be used to alter one or more of the physical properties of thecationic polymer composition.

In order to be an effective ion-sensitive or triggerable cationicpolymer or cationic polymer formulation suitable for use in flushable orwater-dispersible personal care products, the formulations shoulddesirably be (1) functional; i.e., maintain wet strength undercontrolled conditions and dissolve or disperse rapidly in soft or hardwater, such as found in toilets and sinks around the world; (2) safe(not toxic); and (3) relatively economical. In addition to the foregoingfactors, the ion-sensitive or triggerable formulations when used as abinder composition for a non-woven substrate, such as a wet wipe,desirably should be (4) processable on a commercial basis; i.e., may beapplied relatively quickly on a large scale basis, such as by spraying(which thereby requires that the binder composition have a relativelylow viscosity at high shear); and (5) provide acceptable levels of sheetor substrate wettability. The wetting composition with which the wetwipes of the present invention are treated can provide some of theforegoing advantages, and, in addition, can provide one or more of (6)improved skin care, such as reduced skin irritation or other benefits,(7) improved tactile properties, and (8) promote good cleaning byproviding a balance in use between friction and lubricity on the skin(skin glide). The ion-sensitive or triggerable cationic polymers andpolymer formulations of the present invention and articles madetherewith, especially wet wipes comprising particular wettingcompositions set forth below, can meet many or all of the abovecriteria. Of course, it is not necessary for all of the advantages ofthe preferred embodiments of the present invention to be met to fallwithin the scope of the present invention.

Ion-sensitive Cationic Polymer Compositions

The ion-sensitive cationic polymers of the present invention may beformed from two, three or four different monomers. The copolymers of thepresent invention are the polymerization product of a cationic monomerand at least one hydrophobic monomer. The terpolymers or tetrapolymersof the present invention are the polymerization products of a cationicmonomer, at least one hydrophobic monomer and optionally at least onehydrophilic monomer or water-soluble nonionic monomer.

The preferred cationic polymer in the ion-sensitive cationic polymers ofthe present invention is [2-(methacryloyloxy)ethyl] trimethyl ammoniumchloride.

Suitable hydrophobic monomers for use in the ion-sensitive cationicpolymers of the present invention include, but are not limited to, alkylacrylates, such as, butyl acrylate, 2-ethylhexyl acrylate, ethylacrylate, lauryl acrylate, and hexadecyl acrylate. Methacrylate analogsof alkyl acrylates are also suitable.

Suitable hydrophilic monomers or water-soluble nonionic monomers for usein the ion-sensitive cationic polymers of the present invention include,but are not limited to, acrylamide and methacrylamide based monomers,such as acrylamide, N,N-dimethyl acrylamide, N-ethyl acrylamide,N-isopropyl acrylamide, and hydroxymethyl acrylamide; and acrylate ormethacrylate based monomers include, such as, hydroxyalkyl acrylates andhydroxyalkyl methacrylates, such as hydroxyethyl methacrylate,hydroxyethyl acrylate; polyalkoxyl acrylates, such as polyethyleneglycolacrylates and polyalkoxyl methacrylates, such as polyethyleneglycolmethacrylates (“PEG-MA”). Other suitable hydrophilic monomers orwater-soluble nonionic monomers for use in the ion-sensitive cationicpolymers of the present invention include, but are not limited to,N-vinylpyrrolidinone; and N-vinylformamide.

A preferred quaternary polymer of the present invention is thepolymerization product of the following four monomers: acrylamide, butylacrylate, 2-ethylhexyl acrylate and [2-(methacryloyloxy)ethyl] trimethylammonium chloride. A preferred terpolymer of the present invention isformed from three different monomers: butyl acrylate, 2-ethylhexylacrylate and [2-(methacryloyloxy)ethyl] trimethyl ammonium chloride. Apreferred copolymer of the present invention is the polymerizationproduct of [2-(methacryloyloxy)ethyl] trimethyl ammonium chloride andbutyl acrylate or 2-ethylhexyl acrylate. An especially preferredterpolymer of the present invention is the polymerization product of[2-(methacryloyloxy)ethyl] trimethyl ammonium chloride and butylacrylate and 2-ethylhexyl acrylate. Acrylamide,[2-(methacryloyloxy)ethyl] trimethyl ammonium chloride, butyl acrylateand 2-ethylhexyl acrylate are all commercially available from AldrichChemical, Milwaukee, Wis.

For the ion-sensitive quaternary polymer made from acrylamide, butylacrylate, 2-ethylhexyl acrylate and [2-(methacryloyloxy)ethyl] trimethylammonium chloride, the mole percent of monomer in the quaternary polymeris as follows: about 35 to less than 80 mole percent acrylamide; greaterthan 0 to about 45 mole percent butyl acrylate; greater than 0 to about65 mole percent 2-ethylhexyl acrylate; and greater than 0 to about 20mole percent [2-(methacryloyloxy)ethyl] trimethyl ammonium chloride.More specifically, the mole percent of monomers in the quaternarypolymer is from about 50 to about 67 mole percent acrylamide; from about15 to about 28 mole percent butyl acrylate; from about 7 to about 15mole percent 2-ethylhexyl acrylate; and from greater than 0 to about 10mole percent [2-(methacryloyloxy)ethyl] trimethyl ammonium chloride.Most specifically, the mole percent of monomers in the quaternarypolymer is from about 57 to about 66 mole percent acrylamide; from about15 to about 28 mole percent butyl acrylate; from about 7 to about 13mole percent 2-ethylhexyl acrylate; and about 1 to about 6 mole percent[2-(methacryloyloxy)ethyl] trimethyl ammonium chloride.

For the ion-sensitive co- and terpolymer made from butyl acrylate,2-ethylhexyl acrylate and [2-(methacryloyloxy)ethyl] trimethyl ammoniumchloride, the mole percent of monomer in the terpolymer is as follows:from 0 to about 90 mole percent butyl acrylate; from 0 to about 75 molepercent 2-ethylhexyl acrylate; and from 5 to about 60 mole percent[2-(methacryloyloxy)ethyl] trimethyl ammonium chloride.

The ion-sensitive terpolymers and quaternary polymers of the presentinvention may have an average molecular weight, which varies dependingon the ultimate use of the polymer. The quaternary polymers of thepresent invention have a weight average molecular weight ranging fromabout 10,000 to about 5,000,000. More specifically, the quaternarypolymers of the present invention have a weight average molecular weightranging from about 25,000 to about 2,000,000, or, more specificallystill, from about 200,000 to about 1,000,000. The terpolymers of thepresent invention have a weight average molecular weight ranging fromabout 10,000 to about 5,000,000. More specifically, the terpolymers ofthe present invention have a weight average molecular weight rangingfrom about 25,000 to about 2,000,000, or, more specifically still, fromabout 200,000 to about 1,000,000.

The ion-sensitive terpolymers and quaternary polymers of the presentinvention may be prepared according to a variety of polymerizationmethods, desirably a solution polymerization method. Suitable solventsfor the polymerization method include, but are not limited to, loweralcohols such as methanol, ethanol and propanol; a mixed solvent ofwater and one or more lower alcohols mentioned above; and a mixedsolvent of water and one or more lower ketones such as acetone or methylethyl ketone.

In the polymerization methods of the present invention, any free radicalpolymerization initiator may be used. Selection of a particularinitiator may depend on a number of factors including, but not limitedto, the polymerization temperature, the solvent, and the monomers used.Suitable polymerization initiators for use in the present inventioninclude, but are not limited to, 2,2′-azobisisobutyronitrile,2,2′-azobis(2-methylbutyronitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(2-amidinopropane)dihydrochloride,2,2′-azobis(N,N′-dimethyleneisobutylamidine), potassium persulfate,ammonium persulfate, and aqueous hydrogen peroxide. The amount ofpolymerization initiator may desirably range from about 0.01 to 5 weightpercent based on the total weight of monomer present.

The polymerization temperature may vary depending on the polymerizationsolvent, monomers, and initiator used, but in general, ranges from about20° C. to about 90° C. Polymerization time generally ranges from about 2to about 8 hours.

In a further embodiment of the present invention, the above-describedion-sensitive cationic polymer formulations are used as binder materialsfor flushable and/or non-flushable products. In order to be effective asa binder material in flushable products throughout the United States,the ion-sensitive polymer formulations of the present invention remainstable and maintain their integrity while dry or in relatively highconcentrations of monovalent ions, but become soluble in watercontaining up to about 200 ppm or more divalent ions, especially calciumand magnesium. Desirably, the ion-sensitive cationic polymerformulations of the present invention are insoluble in a salt solutioncontaining at least about 2 weight percent of one or more inorganicand/or organic salts containing monovalent and/or multivalent ions. Moredesirably, the ion-sensitive cationic polymer formulations of thepresent invention are insoluble in a salt solution containing from about2 weight percent to about 5 weight percent of one or more inorganicand/or organic salts containing monovalent and/or multivalent ions. Evenmore desirably, the ion-sensitive polymer formulations of the presentinvention are insoluble in salt solutions containing from about 2 weightpercent to about 4 weight percent of one or more inorganic and/ororganic salts containing monovalent and/or multivalent ions. Suitablemonovalent ions include, but are not limited to, Na⁺ ions, K⁺ ions, Li⁺ions, NH₄ ⁺ ions, low molecular weight quaternary ammonium compounds(e.g., those having fewer than 5 carbons on any side group), and acombination thereof. Suitable multivalent ions include, but are notlimited to, Zn²⁺ and Ca²⁺.

Based on a recent study conducted by the American Chemical Society,water hardness across the United States varies greatly, with CaCO₃concentration ranging from near zero for soft water to about 500 ppmCaCO₃ (about 200 ppm Ca²⁺ ion) for very hard water. To ensure polymerformulation dispersibility across the country (and throughout the wholeworld), the ion-sensitive cationic polymer formulations of the presentinvention are desirably soluble in water containing up to about 50 ppmCa²⁺ and/or Mg²⁺ ions. More desirably, the ion-sensitive cationicpolymer formulations of the present invention are soluble in watercontaining up to about 100 ppm Ca²⁺ and/or Mg²⁺ ions. Even moredesirably, the ion-sensitive cationic polymer formulations of thepresent invention are soluble in water containing up to about 150 ppmCa²⁺ and/or Mg²⁺ ions. Even more desirably, the ion-sensitive cationicpolymer formulations of the present invention are soluble in watercontaining up to about 200 ppm Ca²⁺ and/or Mg²⁺ ions.

Ion-Specific Cationic Polymer Compositions

The above-described ion-sensitive polymer compositions when used as abinder for woven or nonwoven substrates, such as wet wipes, helpsmaintain strength in the dry state, or in the wet state by iontriggerability. A high concentration of salt insolubilizes the bindersand allows it to function as an adhesive for the web. This effect isreferred to as “salting out.” The above disclosures identify usefulion-sensitive polymer compositions as well as useful polymer/saltcombinations, which allow for high strength in-use and under storageconditions, but allow the web to break apart in the toilet when the saltconcentration falls below the critical level. As a part of the presentinvention, it has been discovered that a broader range of polymercomposition may be useful in such triggerable applications, but themechanism by which those compositions are rendered triggerable ismediated by the salt concentration and type. Thus, ion-specific triggersystems have been discovered that depend on the nature of the cationicpolymer, the cationic species of the salt and the anionic species of thesalt. In addition, it has been discovered that strength/dispersibilityare closely mediated by both ion types. These new cationic polymerbinder/salt combinations can be used to provide ion-specific triggersystems that are not only pH independent and relatively insensitive towater hardness, but function at much lower levels of added salt than theprevious systems. As used herein, the ion-sensitive polymers andion-specific polymers of the present invention will both be referred toas triggerable polymers.

The ion-specific cationic polymers of the present invention comprise 1)a cationic monomer, 2) at least one water insoluble, hydrophobicmonomer, and optionally, 3) a hydrophilic and/or water-soluble nonionicmonomer. The cationic monomers useful in the present invention includequaternary ammonium monomers, including, but not limited to, cationicmonomer is selected from [2-(methacryloyloxy)ethyl] trimethyl ammoniumchloride, (3-acrylamidopropyl) trimethylammonium chloride,N,N-diallyldimethylammonium chloride, acryloxyethyltrimethyl ammoniumchloride, acryloxyethyldimethylbenzyl ammonium chloride,methacryloxyethyldimethyl ammonium chloride,methacryloxyethyldimethylbenzylammonium chloride and quaternized vinylpyridine. Other vinyl functional monomers which when copolymerized witha water insoluble hydrophobic monomer form ionomers in the presence ofdivalent metal complex anions are also useful in the present invention.

The water insoluble hydrophobic monomers useful in the present inventioninclude n-butyl acrylate and 2-ethylhexyl acrylate. Other n-alkyl orbranched alkyl, acrylamido, acrylic esters and other vinyl functionalmonomers which when copolymerized with the cationic monomer formionomers or ionomer-like structures in the presence of divalent metalcomplex anions are also useful in the present invention.

The hydrophilic and/or water-soluble nonionic monomer useful in thepresent invention include (meth)-acrylamide, substituted(meth)acrylamides, such as diacetone acrylamide, hydroxyalkyl(meth)-acrylate, hydroxyalkyl acrylates, such as hydroxyethyl acrylateor hydroxyethyl methacrylate (HEMA); polyethyleneglycol acrylates,polyethyleneglycol methacrylates, and vinyl pyrrolidone. Other vinylfunctional monomers which when copolymerized with the water insolublehydrophobic monomer and the cationic monomer form ionomers in thepresence of divalent metal complex anions are also useful in the presentinvention.

The key to developing a successful ion-specific cationic polymer binderis to control the balance of the hydrophilic and hydrophobic monomersthrough a careful study of varying polymer compositions. Also,examination and observation of the binder's performance with specificcation and anion types as shown in the examples below has lead to thedevelopment of a proposed mechanism. Without wanting to be limited inany way by the proposed mechanism, applicants believe that theion-specific polymer compositions of the present invention operate asfollows. These results shown below indicate “ion specific” interactionsrather than the “salting-out” effect seen in previous systems. Althoughionic strength may play a role, the data presented here clearlyindicates a new type of trigger mechanism based on hydrophobicassociations and ion-specific interactions. The nature of this mechanismhas been poorly understood until recently. It is believed that certaindivalent metal ions, such as Zn²⁺, Ca²⁺ and Mg²⁺, form complex ions insolution with halogen anions, such as (ZnCl₄)²⁻ (F. Albert Cotton andGeoffrey William, Advanced Inorganic Chemistry, John Wiley and Sons.1980). These complex ions have been isolated as the salts of largecations, such as quaternary ammonium ions. In addition, theseinteractions may become stronger in media of low dielectric constants.Ca²⁺ and Mg²⁺, do not typically form complexes in water, but do so inlower ketones and alcohols (i.e., at lower dielectric constant).

Therefore, it is believed the mechanism relies upon divalent metal ionsthat may form complex anions in the presence of the quaternary ammoniumgroups of the cationic co- and terpolymers. It is believed that thesecomplex ions may “bridge” quaternary ammonium groups on the same polymermolecule or on other molecules and lead to a psuedo-crosslinkedstructure. Additionally, it is believed that these complex ion clustersorganize into ionomer or ionomer-like domains, giving an overallmorphology that results in good web strength in relatively low saltconcentrations. Since the formation of the complex anions is highlydependant on the metal and counterion concentrations, the web becomere-dispersible upon dilution with water that may contain other ions,even relatively high concentrations of other ions, such as found in hardwater.

For the ion-specific copolymer made from a cationic monomer and a waterinsoluble, hydrophobic monomer, the mole percent of monomer in thecopolymer is as follows: about 10 to less than 50 mole percent cationicmonomer; and greater than 50 to about 90 mole percent water insoluble,hydrophobic monomer. More specifically, the mole percent of monomers inthe copolymer is from about 15 to about 25 mole percent cationicmonomer; and from about 70 to about 85 mole percent water insoluble,hydrophobic monomer. Most specifically, the mole percent of monomers inthe copolymer is from about 20 mole percent cationic monomer; and about80 mole percent water insoluble, hydrophobic monomer.

For the ion-specific terpolymer made from a cationic polymer, a waterinsoluble hydrophobic monomer and a water soluble or hydrophilicmonomer, the mole percent of monomer in the terpolymer is as follows:about 5 to less than 50 mole percent cationic monomer; from about 30 toabout 90 mole percent water insoluble hydrophobic monomer; and fromabout 10 to about 60 mole percent water soluble or hydrophilic monomer.

The ion-specific copolymers and terpolymers of the present invention mayhave an average molecular weight, which varies depending on the ultimateuse of the polymer. The copolymers and terpolymers of the presentinvention have a weight average molecular weight ranging from about10,000 to about 5,000,000. More specifically, the copolymers andterpolymers of the present invention have a weight average molecularweight ranging from about 25,000 to about 2,000,000, or, morespecifically still, from about 200,000 to about 1,000,000.

The ion-specific copolymers and terpolymers of the present invention maybe prepared according to the same free radical polymerization methodsdescribed above for the ion-sensitive cationic polymer.

As stated above, the mechanism of the ion-specific cationic polymerrelies upon the interaction of the polymer cation and the amount andspecific type of anion in a wetting solution. It has been discovered asa part of the present invention that the anion must be a divalent metalion that forms a complex anion. Furthermore, the counterion of thedivalent metal ion also seems to plays a role in the operability of thepresent invention. The divalent metal ions that are useful in thepresent invention include Zn²⁺, Ca²⁺ and Mg²⁺. The counter ion for thedivalent metal ion that are useful in the present invention includehalogen ion, particularly Cl⁻, Br⁻ and I⁻. Thus, salts that are usefulin the present invention include ZnCl₂, MgCl₂, and CaCl₂. Other divalentmetal salts that form complex anions in the presence of the quaternaryammonium group of the cationic polymer are also useful in the presentinvention.

Again, without wishing to be bound by a proposed mechanism, it appearsthat certain divalent ions, such as Zn²⁺, may form complex ions insolution with halogen anions, such as (ZnCl₄)²⁻ (F. Albert Cotton andGeoffrey William, Advanced Inorganic Chemistry, John Wiley and Sons.1980). These complex ions have been isolated as the salts of largecations, such as quaternary ammonium ions. In addition, theseinteractions may become stronger in media of low dielectric constants.Ca²⁺ and Mg²⁺, do not typically form complexes in water, but do so inlower ketones and alcohols (i.e., at lower dielectric constant).

Therefore, the mechanism is believed to involve divalent metal ions thatform complex anions in the presence of the quaternary ammonium groups ofthe co- and terpolymers. It is believed that these complex ions “bridge”quaternary ammonium groups on the same polymer molecule or on othermolecules and lead to a psuedo-crosslinked structure. Additionally, itis believed that these complex ion clusters organized into ionomers,giving an overall morphology that results in good web strength insolutions containing specific amounts and types of salts. Since theformation of the complex anions is highly dependant on the metal andcounterion concentrations, the web become re-dispersible upon dilutionwith water that does not contain the critical amount of these complexanions, but may contain other mono or divalent ions, such as found inhard or soft water.

In a further embodiment of the present invention, the above-describedion-specific cationic polymer formulations are used as binder materialsfor flushable and/or non-flushable products. In order to be effective asa binder material in flushable products throughout the United States,the ion-specific cationic polymer formulations of the present inventionremain stable and maintain their integrity while dry or in relativelyhigh concentrations of ions, but become soluble in water containing upto about 200 ppm or more divalent ions, especially calcium, magnesiumand sulfonate ions. Desirably, the ion-specific cationic polymerformulations of the present invention are insoluble in a solutioncontaining at least about 0.5 weight percent of one or more divalentmetal salts capable of forming complex anions. More desirably, theion-specific cationic polymer formulations of the present invention areinsoluble in a solution containing from about 1 weight percent to about5 weight percent of one or more divalent metal salts capable of formingcomplex anions. Even more desirably, the ion-specific cationic polymerformulations of the present invention are insoluble in solutionscontaining from about 2 weight percent to about 4 weight percent of oneor more divalent metal salts capable of forming complex anions.

To ensure polymer formulation dispersibility across the country (andthroughout the whole world), the ion-specific cationic polymerformulations of the present invention are desirably soluble in watercontaining up to about 50 ppm Ca²⁺ and/or Mg²⁺ ions. More desirably, theion-specific cationic polymer formulations of the present invention aresoluble in water containing up to about 100 ppm Ca²⁺ and/or Mg²⁺ ions.Even more desirably, the ion-specific cationic polymer formulations ofthe present invention are soluble in water containing up to about 150ppm Ca²⁺ and/or Mg²⁺ ions. Even more desirably, the ion-specificcationic polymer formulations of the present invention are soluble inwater containing up to about 200 ppm Ca²⁺ and/or Mg²⁺ ions.

Co-binder Polymers

As stated above, the cationic polymer formulations of the presentinvention are formed from a single triggerable polymer or a combinationof two or more different polymers, wherein at least one polymer is atriggerable polymer. The second polymer may be a co-binder polymer. Aco-binder polymer is of a type and in an amount such that when combinedwith the triggerable polymer, the co-binder polymer desirably is largelydispersed in the triggerable polymer; i.e., the triggerable polymer isdesirably the continuous phase and the co-binder polymer is desirablythe discontinuous phase. Desirably, the co-binder polymer can also meetseveral additional criteria. For example, the co-binder polymer can havea glass transition temperature; i.e., T_(g), that is lower than theglass transition temperature of the triggerable polymer. Furthermore oralternatively, the co-binder polymer can be insoluble in water, or canreduce the shear viscosity of the triggerable polymer. The co-binder canbe present at a level relative to the solids mass of the triggerablepolymer of about 45% or less, specifically about 30% or less, morespecifically about 20% or less, more specifically still about 15% orless, and most specifically about 10% or less, with exemplary ranges offrom about 1% to about 45% or from about 25% to about 35%, as well asfrom about 1% to about 20% or from about 5% to about 25%. The amount ofco-binder present should be low enough, for co-binders with thepotential to form water insoluble bonds or films, that the co-binderremains a discontinuous phase unable to create enough crosslinked, orinsoluble bonds, to jeopardize the dispersibility of the treatedsubstrate. In one embodiment, the polymer formulation of the presentinvention can comprise about 75 weight percent triggerable polymer andabout 25 weight percent co-binder.

Desirably, but not necessarily, the co-binder polymer when combined withthe triggerable polymer will reduce the shear viscosity of thetriggerable polymer to such an extent that the combination of thetriggerable polymer and the co-binder polymer is sprayable. By sprayableis meant that the polymer can be applied to a nonwoven fibrous substrateby spraying and the distribution of the polymer across the substrate andthe penetration of the polymer into the substrate are such that thepolymer formulation is uniformly applied to the substrate.

The co-binder polymer can be in the form of an emulsion latex. Thesurfactant system used in such a latex emulsion should be such that itdoes not substantially interfere with the dispersibility of thetriggerable polymer.

In some embodiments, the combination of the triggerable polymer and theco-binder polymer reduces the stiffness of the article to which it isapplied compared to the article with just the triggerable polymer. Ithas been found that when the triggerable polymer is applied to anonwoven substrate, such as an air laid layer of wood pulp, for thepurpose of forming a wet wipe, the nonwoven sheet can have anundesirable amount of stiffness that is detrimental to the dry productfeel or to the handling of the dry web during processing, when thebrittleness of the dry substrate can harm runnability. By combining thetriggerable polymer and the co-binder polymer, the stiffness of sucharticles can be reduced.

The co-binder polymer of the present invention can have an averagemolecular weight, which varies depending on the ultimate use of thepolymer. Desirably, the co-binder polymer has a weight average molecularweight ranging from about 500,000 to about 200,000,000. More desirably,the co-binder polymer has a weight average molecular weight ranging fromabout 500,000 to about 100,000,000.

Co-binder polymers that can meet many or all of the foregoing criteriainclude, but are not limited to, poly(ethylene-vinyl acetate),poly(styrene-butadiene), poly(styrene-acrylic), a vinyl acrylicterpolymer, neoprene, a polyester latex, an acrylic emulsion latex, polyvinyl chloride, ethylene-vinyl chloride copolymer, a carboxylated vinylacetate latex, and the like, all of which can be non-crosslinking (e.g.,devoid of N-methylol acrylamide or other crosslinkers), crosslinking, orpotentially crosslinking (i.e., prepared with a crosslinker present) butnot substantially crosslinked in the final product.

A particularly preferred non-crosslinking poly(ethylene-vinyl acetate)is Dur-O-Set® RB available from National Starch and Chemical Co.,Bridgewater, N.J. A particularly preferred non-crosslinkingpoly(styrene-butadiene) is Rovene® 4817 available from Mallard CreekPolymers, Charlotte, N.C. A particularly preferred non-crosslinkingpoly(styrene-acrylic) is Rhoplex® NM 1715K available from Rohm and Haas,Philadelphia, Pa.

When a latex co-binder, or any potentially crosslinkable co-binder isused, the latex should be prevented from forming substantialwater-insoluble bonds that bind the fibrous substrate together andinterfere with the dispersibility of the article. Thus, the latex can befree of crosslinking agents, such as NMA, or free of catalyst for thecrosslinker, or both. Alternatively, an inhibitor can be added thatinterferes with the crosslinker or with the catalyst such thatcrosslinking is impaired even when the article is heated to normalcrosslinking temperatures. Such inhibitors can include free radicalscavengers, methyl hydroquinone, t-butylcatechol, pH control agents suchas potassium hydroxide, and the like. For some latex crosslinkers, suchas N-methylol-acrylamide (NMA), for example, elevated pH such as a pH of8 or higher can interfere with crosslinking at normal crosslinkingtemperatures (e.g., about 130° C. or higher). Also alternatively, anarticle comprising a latex co-binder can be maintained at temperaturesbelow the temperature range at which crosslinking takes place, such thatthe presence of a crosslinker does not lead to crosslinking, or suchthat the degree of crosslinking remains sufficiently low that thedispersibility of the article is not jeopardized. Also alternatively,the amount of crosslinkable latex can be kept below a threshold levelsuch that even with crosslinking, the article remains dispersible. Forexample, a small quantity of crosslinkable latex dispersed as discreteparticles in an ion-sensitive binder can permit dispersibility even whenfully crosslinked. For the later embodiment, the amount of latex can bebelow about 20 weight percent, and, more specifically, below about 15weight percent relative to the ion-sensitive binder.

Latex compounds, whether crosslinkable or not, need not be theco-binder. SEM micrography of successful ion-sensitive binder films withuseful non-crosslinking latex emulsions dispersed therein has shown thatthe latex co-binder particles can remain as discrete entities in theion-sensitive binder, possibly serving in part as filler material. It isbelieved that other materials could serve a similar role, including adispersed mineral or particulate filler in the triggerable binder,optionally comprising added surfactants/dispersants. For example, in oneenvisioned embodiment, freeflowing Ganzpearl PS-8F particles fromPresperse, Inc. (Piscataway, N.J.), a styrene/divinylbenzene copolymerwith about 0.4 micron particles, can be dispersed in a triggerablebinder at a level of about 2 to 10 weight percent to modify themechanical, tactile, and optical properties of the triggerable binder.Other filler-like approaches may include microparticles, microspheres,or microbeads of metal, glass, carbon, mineral, quartz, and/or plastic,such as acrylic or phenolic, and hollow particles having inert gaseousatmospheres sealed within their interiors. Examples include EXPANCELphenolic microspheres from Expancel of Sweden, which expandsubstantially when heated, or the acrylic microspheres known as PM 6545available from PQ Corporation of Pennsylvania. Foaming agents, includingCO₂ dissolved in the triggerable binder, could also provide helpfuldiscontinuities as gas bubbles in the matrix of an triggerable binder,allowing the dispersed gas phase in the triggerable binder to serve asthe co-binder. In general, any compatible material that is not misciblewith the binder, especially one with adhesive or binding properties ofits own, can be used as the co-binder, if it is not provided in a statethat imparts substantial covalent bonds joining fibers in a way thatinterferes with the water-dispersibility of the product. However, thosematerials that also provide additional benefits, such as reduced sprayviscosity, can be especially preferred. Adhesive co-binders, such aslatex that do not contain crosslinkers or contain reduced amounts ofcrosslinkers, have been found to be especially helpful in providing goodresults over a wide range of processing conditions, including drying atelevated temperatures.

As stated above, the T_(g) of the co-binder polymer can be lower thanthe T_(g) of the triggerable polymer, which is believed to improve theflexibility of the treated substrate, especially in the dry state. InTable 1 shown below is a comparison of the glass transition temperatureof some of the preferred polymers useful in the present invention.

TABLE 1 Glass Transition Temperatures For Select Polymers Polymer GlassTransition Temperature - Tg Cationic Sample #1 from 15° C. Example 2below Cationic Sample #6 from 24° C. Example 2 below Rhoplex NW −6° C.1715K (dry) Rovene 4817 (dry) −4° C. Elite 33 (dry) −10° C. Elite 22(dry) −15° C.

In an alternate embodiment, the triggerable polymer formulations of thepresent invention comprises about 55 to about 95 weight percenttriggerable polymer and about 5 to about 45 weight percentpoly(ethylene-vinyl acetate). More desirably, the triggerable polymerformulations of the present invention comprises about 75 weight percenttriggerable polymer and about 25 weight percent poly(ethylene-vinylacetate).

As stated above, useful co-binder polymers can include a variety ofcommercial latex emulsions, including those selected from the Rovene®series (styrene butadiene lattices available from Mallard Creek Polymersof Charlotte, N.C.), the Rhoplex® latices of Rohm and Haas Company, andthe Elite® latices of National Starch. Polymer emulsions or dispersionsgenerally comprise small polymer particles, such as crosslinkableethylene vinyl acetate copolymers, typically in spherical form,dispersed in water and stabilized with surface active ingredients, suchas low molecular weight emulsifiers or high molecular weight protectivecolloids. Care must be taken in selecting the proper emulsion system sothat the emulsion will not interact with the cationic binder tointerfere with the trigger property.

These liquid binders can be applied to airlaid webs or other substratesby methods known in the art of binder treatment for nonwoven webs,including spray or foam application, flooded nip impregnation, curtaincoating, etc., followed by drying. In general, a wide variety of latexcompounds and other resins or emulsions can be considered, includingvinyl acetate copolymer latices, such as 76 RES 7800 from Union OilChemicals Divisions and Duroset RB®, Resyn® 25-1103, Resyn® 25-1109,Resyn® 25-1119, and Resyn® 25-1189 from National Starch and ChemicalCorporation, ethylene-vinyl acetate copolymer emulsions, such asAirflex® ethylene-vinylacetate from Air Products and Chemicals Inc.,acrylic-vinyl acetate copolymer emulsions, such as Rhoplex® AR-74 fromRohm and Haas Company, Synthemul® 97-726 from Reichhold Chemicals Inc.,Resyn® 25-1140, 25-1141, 25-1142, and Resyn-6820 from National Starchand Chemical Corporation, vinyl acrylic terpolymer latices, such as 76RES 3103 from Union Oil Chemical Division, and Resyn® 251110 fromNational Starch and Chemical Corporation, acrylic emulsion latices, suchas Rhoplex® B-15J, Rhoplex® P-376, Rhoplex® TR-407, Rhoplex® E-940,Rhoplex® TR934, Rhoplex® TR-520, Rhoplex® HA-24, and Rhoplex® NW1825from Rohm and Haas Company, and Hycar® 2600 X 322, Hycar® 2671, Hycar®2679, Hycar® 26120, and Hycar® 2600 X347 from B. F. Goodrich ChemicalGroup, styrene-butadiene latices, such as 76 RES 4100 and 76 RES 8100available from Union Oil Chemicals Division, Tylac® resin emulsion68-412, Tylac® resin emulsion 68-067, 68-319, 68-413, 68-500, 68-501,available from Reichhold Chemical Inc., and DL6672A, DL6663A, DL6638A,DL6626A, DL6620A, DL615A, DL617A, DL620A, DL640A, DL650A available fromDow Chemical Company; and rubber latices, such as neoprene availablefrom Serva Biochemicals; polyester latices, such as Eastman AQ 29Davailable from Eastman Chemical Company; vinyl chloride latices, such asGeon® 352 from B. F. Goodrich Chemical Group; ethylene-vinyl chloridecopolymer emulsions, such as Airflex® ethylene-vinyl chloride from AirProducts and Chemicals; polyvinyl acetate homopolymer emulsions, such asVinac® from Air Products and Chemicals; carboxylated vinyl acetateemulsion resins, such as Synthemul® synthetic resin emulsions 40-502,40-503, and 97-664 from Reichhold Chemicals Inc. and Polyco® 2149, 2150,and 2171 from Rohm and Haas Company. Silicone emulsions and binders canalso be considered.

The co-binder polymer can comprise surface active compounds that improvethe wettability of the substrate after application of the bindermixture. Wettability of a dry substrate that has been treated with atriggerable polymer formulation can be a problem in some embodiments,because the hydrophobic portions of the triggerable polymer formulationcan become selectively oriented toward the air phase during drying,creating a hydrophobic surface that can be difficult to wet when thewetting composition is later applied unless surfactants are added to thewetting composition. Surfactants, or other surface active ingredients,in co-binder polymers can improve the wettability of the dried substratethat has been treated with a triggerable polymer formulation.Surfactants in the co-binder polymer should not significantly interferewith the triggerable polymer formulation. Thus, the binder shouldmaintain good integrity and tactile properties in the pre-moistenedwipes with the surfactant present.

In one embodiment, an effective co-binder polymer replaces a portion ofthe triggerable polymer formulation and permits a given strength levelto be achieved in a pre-moistened wipe with at least one of lowerstiffness, better tactile properties (e.g., lubricity or smoothness), orreduced cost, relative to an otherwise identical pre-moistened wipelacking the co-binder polymer and comprising the triggerable polymerformulation at a level sufficient to achieve the given tensile strength.

Other Co-binder Polymers

The Dry Emulsion Powder (DEP) binders of Wacker Polymer Systems(Burghausen, Germany) such as the VINNEK® system of binders, can beapplied in some embodiments of the present invention. These areredispersible, free flowing binder powders formed from liquid emulsions.Small polymer particles from a dispersion are provided in a protectivematrix of water soluble protective colloids in the form of a powderparticle. The surface of the powder particle is protected against cakingby platelets of mineral crystals. As a result, polymer particles thatonce were in a liquid dispersion are now available in a free flowing,dry powder form that can be redispersed in water or turned into swollen,tacky particles by the addition of moisture. These particles can beapplied in highloft nonwovens by depositing them with the fibers duringthe airlaid process, and then later adding 10% to 30% moisture to causethe particles to swell and adhere to the fibers. This can be called the“chewing gum effect,” meaning that the dry, non-tacky fibers in the webbecome sticky like chewing gum once moistened. Good adhesion to polarsurfaces and other surfaces is obtained. These binders are available asfree flowing particles formed from latex emulsions that have been driedand treated with agents to prevent cohesion in the dry state. They canbe entrained in air and deposited with fibers during the airlaidprocess, or can be applied to a substrate by electrostatic means, bydirect contact, by gravity feed devices, and other means. They can beapplied apart from the binder, either before or after the binder hasbeen dried. Contact with moisture, either as liquid or steam, rehydratesthe latex particles and causes them to swell and to adhere to thefibers. Drying and heating to elevated temperatures (e.g., above 160°C.) causes the binder particles to become crosslinked and waterresistant, but drying at lower temperatures (e.g., at 110° C. or less)can result in film formation and a degree of fiber binding withoutseriously impairing the water dispersibility of the pre-moistened wipes.Thus, it is believed that the commercial product can be used withoutreducing the amount of crosslinker by controlling the curing of theco-binder polymer, such as limiting the time and temperature of dryingto provide a degree of bonding without significant crosslinking.

As pointed out by Dr. Klaus Kohlhammer in “New Airlaid Binders,”Nonwovens Report International, September 1999, issue 342, pp. 20-22,28-31, dry emulsion binder powders have the advantage that they caneasily be incorporated into a nonwoven or airlaid web during formationof the web, as opposed to applying the material to an existingsubstrate, permitting increased control over placement of the co-binderpolymer. Thus, a nonwoven or airlaid web can be prepared already havingdry emulsion binders therein, followed by moistening when theion-sensitive polymer formulation solution is applied, whereupon the dryemulsion powder becomes tacky and contributes to binding of thesubstrate. Alternatively, the dry emulsion powder can be entrapped inthe substrate by a filtration mechanism after the substrate has beentreated with triggerable binder and dried, whereupon the dry emulsionpowder is rendered tacky upon application of the wetting composition.

In another embodiment, the dry emulsion powder is dispersed into thetriggerable polymer formulation solution either by application of thepowder as the triggerable polymer formulation solution is being sprayedonto the web or by adding and dispersing the dry emulsion powderparticles into the triggerable polymer formulation solution, after whichthe mixture is applied to a web by spraying, by foam applicationmethods, or by other techniques known in the art.

Binder Formulations and Fabrics Containing the Same

The triggerable polymer formulations of the present invention may beused as binders. The triggerable binder formulations of the presentinvention may be applied to any fibrous substrate. The binders areparticularly suitable for use in water-dispersible products. Suitablefibrous substrates include, but are not limited to, nonwoven and wovenfabrics. In many embodiments, particularly personal care products,preferred substrates are nonwoven fabrics. As used herein, the term“nonwoven fabric” refers to a fabric that has a structure of individualfibers or filaments randomly arranged in a mat-like fashion (includingpapers). Nonwoven fabrics can be made from a variety of processesincluding, but not limited to, air-laid processes, wet-laid processes,hydroentangling processes, staple fiber carding and bonding, andsolution spinning.

The triggerable binder composition may be applied to the fibroussubstrate by any known process of application. Suitable processes forapplying the binder material include, but are not limited to, printing,spraying, electrostatic spraying, coating, flooded nips, metered pressrolls, impregnating or by any other technique. The amount of bindercomposition may be metered and distributed uniformly within the fibroussubstrate or may be non-uniformly distributed within the fibroussubstrate. The binder composition may be distributed throughout theentire fibrous substrate or it may be distributed within a multiplicityof small closely spaced areas. In most embodiments, uniform distributionof binder composition is desired.

For ease of application to the fibrous substrate, the triggerable bindermay be dissolved in water, or in a non-aqueous solvent, such asmethanol, ethanol, acetone, or the like, with water being the preferredsolvent. The amount of binder dissolved in the solvent may varydepending on the polymer used and the fabric application. Desirably, thebinder solution contains up to about 50 percent by weight of bindercomposition solids. More desirably, the binder solution contains fromabout 10 to 30 percent by weight of binder composition solids,especially about 15-25 percent by weight binder composition solids.Plasticizers, perfumes, coloring agents, antifoams, bactericides,preservative, surface active agents, thickening agents, fillers,opacifiers, tackifiers, detackifiers, and similar additives can beincorporated into the solution of binder components, if so desired.

Once the triggerable binder composition is applied to the substrate, thesubstrate is dried by any conventional means. Once dry, the coherentfibrous substrate exhibits improved tensile strength when compared tothe tensile strength of the untreated wet-laid or dry-laid substrates,and yet has the ability to rapidly “fall apart”, or disintegrate whenplaced in soft or hard water having a relatively high multivalent ionicconcentration and agitated. For example, the dry tensile strength of thefibrous substrate may be increased by at least 25 percent as compared tothe dry tensile strength of the untreated substrate not containing thebinder. More particularly, the dry tensile strength of the fibroussubstrate may be increase by at least 100 percent as compared to the drytensile strength of the untreated substrate not containing the binder.Even more particularly, the dry tensile strength of the fibroussubstrate may be increased by at least 500 percent as compared to thedry tensile strength of the untreated substrate not containing thebinder.

A desirable feature of the present invention is that the improvement intensile strength is effected where the amount of binder compositionpresent, “add-on”, in the resultant fibrous substrate represents only asmall portion by weight of the entire substrate. The amount of “add-on”can vary for a particular application; however, the optimum amount of“add-on” results in a fibrous substrate which has integrity while in useand also quickly disperses when agitated in water. For example, thebinder components typically are from about 5 to about 65 percent, byweight, of the total weight of the substrate. More particularly, thebinder components may be from about 10 to about 35 percent, by weight,of the total weight of the substrate. Even more particularly, the bindercomponents may be from about 17 to about 22 percent by weight of thetotal weight of the substrate.

The nonwoven fabrics of the present invention have good in-use tensilestrength, as well as, ion triggerability. Desirably, the nonwovenfabrics of the present invention are abrasion resistant and retainsignificant tensile strength in aqueous solutions containing thespecific amount and type of ions disclosed above. Because of this latterproperty, nonwoven fabrics of the present invention are well suited fordisposable products, such as sanitary napkins, diapers, adultincontinence products, and dry and premoistened wipes (wet wipes), whichcan be thrown in a flush toilet after use in any part of the world.

The fibers forming the fabrics above can be made from a variety ofmaterials including natural fibers, synthetic fibers, and combinationsthereof. The choice of fibers depends upon, for example, the intendedend use of the finished fabric and fiber cost. For instance, suitablefibrous substrates may include, but are not limited to, natural fiberssuch as cotton, linen, jute, hemp, wool, wood pulp, etc. Similarly,regenerated cellulosic fibers, such as viscose rayon and cuprammoniumrayon, modified cellulosic fibers, such as cellulose acetate, orsynthetic fibers, such as those derived from polypropylenes,polyethylenes, polyolefins, polyesters, polyamides, polyacrylics, etc.,alone or in combination with one another, may likewise be used. Blendsof one or more of the above fibers may also be used, if so desired.Among wood pulp fibers, any known papermaking fibers may be used,including softwood and hardwood fibers. Fibers, for example, may bechemically pulped or mechanically pulped, bleached or unbleached, virginor recycled, high yield or low yield, and the like. Mercerized,chemically stiffened or crosslinked fibers may also be used.

Synthetic cellulose fiber types include rayon in all its varieties andother fibers derived from viscose or chemically modified cellulose,including regenerated cellulose and solvent-spun cellulose, such asLyocell. Chemically treated natural cellulosic fibers can be used, suchas mercerized pulps, chemically stiffened or crosslinked fibers, orsulfonated fibers. Recycled fibers, as well as virgin fibers, can beused. Cellulose produced by microbes and other cellulosic derivativescan be used. As used herein, the term “cellulosic” is meant to includeany material having cellulose as a major constituent, and, specifically,comprising at least 50 percent by weight cellulose or a cellulosederivative. Thus, the term includes cotton, typical wood pulps,non-woody cellulosic fibers, cellulose acetate, cellulose triacetate,rayon, thermomechanical wood pulp, chemical wood pulp, debonded chemicalwood pulp, milkweed, or bacterial cellulose.

The triggerable binder of the present invention may also be applied toother fibers or particles. Other fibers that may be treated with thetriggerable binder of the present invention such as fibers made fromcarboxymethyl cellulose, chitin, and chitiosan. The triggerable binderof the present invention may also be applied to particles, such assodium polyacrylate super absorbent particles. Super absorbent particlesare frequently incorporated on or into fibrous substrates used forpersonal care items, especially nonwoven fabrics.

The fiber length is important in producing the fabrics of the presentinvention. In some embodiments, such as flushable products, fiber lengthis of more importance. The minimum length of the fibers depends on themethod selected for forming the fibrous substrate. For example, wherethe fibrous substrate is formed by carding, the length of the fibershould usually be at least about 42 mm in order to insure uniformity.

Where the fibrous substrate is formed by air-laid or wet-laid processes,the fiber length may desirably be about 0.2 to 6 mm. Although fibershaving a length of greater than 50 mm are within the scope of thepresent invention, it has been determined that when a substantialquantity of fibers having a length greater than about 15 mm is placed ina flushable fabric, though the fibers will disperse and separate inwater, their length tends to form “ropes” of fibers, which areundesirable when flushing in home toilets. Therefore, for theseproducts, it is desired that the fiber length be about 15 mm or less sothat the fibers will not have a tendency to “rope” when they are flushedthrough a toilet. Although fibers of various lengths are applicable inthe present invention, desirably fibers are of a length less than about15 mm so that the fibers disperse easily from one another when incontact with water. The fibers, particularly synthetic fibers, can alsobe crimped.

The fabrics of the present invention may be formed from a single layeror multiple layers. In the case of multiple layers, the layers aregenerally positioned in a juxtaposed or surface-to-surface relationshipand all or a portion of the layers may be bound to adjacent layers.Nonwoven webs of the present invention may also be formed from aplurality of separate nonwoven webs wherein the separate nonwoven websmay be formed from single or multiple layers. In those instances wherethe nonwoven web includes multiple layers, the entire thickness of thenonwoven web may be subjected to a binder application or each individuallayer may be separately subjected to a binder application and thencombined with other layers in a juxtaposed relationship to form thefinished nonwoven web.

In one embodiment, the fabric substrates of the present invention may beincorporated into cleansing and body fluid absorbent products, such assanitary napkins, diapers, adult incontinence products, surgicaldressings, tissues, wet wipes, and the like. These products may includean absorbent core, comprising one or more layers of an absorbent fibrousmaterial. The core may also comprise one or more layers of afluid-pervious element, such as fibrous tissue, gauze, plastic netting,etc. These are generally useful as wrapping materials to hold thecomponents of the core together. Additionally, the core may comprise afluid-impervious element or barrier means to preclude the passage offluid through the core and on the outer surfaces of the product.Desirably, the barrier means also is water-dispersible. A film of apolymer having substantially the same composition as the aforesaidwater-dispersible binder is particularly well-suited for this purpose.In accordance with the present invention, the polymer compositions areuseful for forming each of the above-mentioned product componentsincluding the layers of absorbent core, the fluid-pervious element, thewrapping materials, and the fluid-impervious element or barrier means.

The triggerable binder formulations of the present invention areparticularly useful for binding fibers of air-laid nonwoven fabrics.These air-laid materials are useful for body-side liners, fluiddistribution materials, fluid in-take materials, such as a surgematerial, absorbent wrap sheet and cover stock for variouswater-dispersible personal care products. Air-laid materials areparticularly useful for use as a pre-moistened wipe (wet wipe). Thebasis weights for air-laid non-woven fabrics may range from about 20 toabout 200 grams per square meter (“gsm”) with staple fibers having adenier of about 0.5-10 and a length of about 6-15 millimeters. Surge, orin-take, materials need better resiliency and higher loft so staplefibers having about 6 denier or greater are used to make these products.A desirable final density for the surge, or in-take, materials isbetween about 0.025 grams per cubic centimeter (“g/cc”) to about 0.10g/cc. Fluid distribution materials may have a higher density, in thedesired range of about 0.10 to about 0.20 g/cc using fibers of lowerdenier, most desirable fibers have a denier of less than about 1.5.Wipes generally can have a fiber density of about 0.025 g/cc to about0.2 g/cc and a basis weight of about 20 gsm to about 150 gsm;specifically from about 30 to about 90 gsm, and most specifically fromabout 60 gsm to about 65 gsm.

The nonwoven fabrics of the present invention may also be incorporatedinto such body fluid absorbing products as sanitary napkins, diapers,surgical dressings, tissues and the like. In one embodiment, thetriggerable binder is such that it will not dissolve when contacted bybody fluids since the concentration of monovalent ions in the bodyfluids is above the level needed for dissolution; i.e., greater than 2%by weight. The nonwoven fabric retains its structure, softness andexhibits a toughness satisfactory for practical use. However, whenbrought into contact with water having a concentration of multivalentions, such as Ca²⁺ and Mg²⁺ ions, of up to about 200 ppm or more, thebinder disperses. The nonwoven fabric structure is then easily brokenand dispersed in the water.

In one embodiment of the present invention, the in-use tensile strengthof a nonwoven fabric is enhanced by forming the nonwoven fabric with abinder material comprising the triggerable polymer formulation of thepresent invention and subsequently applying either one or moremonovalent and/or multivalent salts to the nonwoven fabric or salts ofdivalent metal ions that form complex anions. The salt may be applied tothe nonwoven fabric by any method known to those of ordinary skill inthe art including, but not limited to, applying a solid powder onto thefabric and spraying a salt solution onto the fabric. The amount of saltmay vary depending on a particular application. However, the amount ofsalt applied to the fabric is typically from about 0.5 weight percent toabout 10 weight percent salt solids based on the total weight of thefabric. The salt-containing fabrics of the present invention may be usedin a variety of fabric applications including, but not limited to,feminine pads, surgical dressings, and diapers.

Those skilled in the art will readily understand that the binderformulations and fibrous substrates of the present invention may beadvantageously employed in the preparation of a wide variety ofproducts, including but not limited to, absorbent personal care productsdesigned to be contacted with body fluids. Such products may onlycomprise a single layer of the fibrous substrate, or may comprise acombination of elements, as described above. Although the binderformulations and fibrous substrates of the present invention areparticularly suited for personal care products, the binder formulationsand fibrous substrates may be advantageously employed in a wide varietyof consumer products.

Unlike other binder systems known in the art, the triggerable polymerformulations of the present invention can be activated as binderswithout the need for elevated temperature. While drying or water removalis useful in achieving a good distribution of the binder in a fibrousweb, elevated temperature, per se, is not essential because the binderdoes not require crosslinking or other chemical reactions with highactivation energy to serve as a binder. Rather, the interaction with asoluble insolubilizing compound, typically a salt, is sufficient tocause the binder to become insoluble; i.e., “salted out” or activated byinteraction between the cation of the polymer and the divalent metalcomplex anion from the salt. Thus, a drying step can be avoided, ifdesired, or replaced with low-temperature water removal operations suchas room-temperature drying or freeze drying. Elevated temperature isgenerally helpful for drying, but the drying can be done at temperaturesbelow what is normally needed to drive crosslinking reactions. Thus, thepeak temperature to which the substrate is exposed or to which thesubstrate is brought can be below any of the following: 180° C., 160°C., 140° C., 120° C., 110° C., 105° C., 100° C., 90° C., 75° C., and 60°C., with an exemplary range for peak web temperature of from about 50°C. to about 110° C., or from about 70° C. to about 140° C. Of course,higher temperatures can be used, but are not necessary in mostembodiments. While polymer systems, such as commercial latex emulsions,may also comprise crosslinkers suited for reaction at temperatures of160° C. or higher, maintaining a lower peak temperature can bebeneficial in preventing development of excessive strength in thepolymer that might otherwise hinder the water dispersibility of thepre-moistened wipe.

Wet Wipe Wetting Composition and Wet Wipes Containing the Same

One particularly interesting embodiment of the present invention is theproduction of pre-moistened wipes, or wet wipes, from theabove-described triggerable binder compositions and fibrous materials.For wipes, the fibrous material may be in the form of a woven ornonwoven fabric; however, nonwoven fabrics are more desirable. Thenonwoven fabric is desirably formed from relatively short fibers, suchas wood pulp fibers. The minimum length of the fibers depends on themethod selected for forming the nonwoven fabric. Where the nonwovenfabric is formed by a wet or dry method, the fiber length is desirablyfrom about 0.1 millimeters to 15 millimeters. Desirably, the nonwovenfabric of the present invention has a relatively low wet cohesivestrength when it is not bonded together by an adhesive or bindermaterial. When such nonwoven fabrics are bonded together by a bindercomposition, which loses its bonding strength in tap water and in sewerwater, the fabric will break up readily by the agitation provided byflushing and moving through the sewer pipes.

The finished wipes may be individually packaged, desirably in a foldedcondition, in a moisture proof envelope or packaged in containersholding any desired number of sheets in a water-tight package with awetting composition applied to the wipe. The finished wipes may also bepackaged as a roll of separable sheets in a moisture-proof containerholding any desired number of sheets on the roll with a wettingcomposition applied to the wipes. The roll can be coreless and eitherhollow or solid. Coreless rolls, including rolls with a hollow center orwithout a solid center, can be produced with known coreless rollwinders, including those of SRP Industry, Inc. (San Jose, Calif.);Shimizu Manufacturing (Japan), and the devices disclosed in U.S. Pat.No. 4,667,890, issued May 26, 1987 to Gietman. Solid-wound corelessrolls can offer more product for a given volume and can be adapted for awide variety of dispensers.

Relative to the weight of the dry fabric, the wipe may desirably containfrom about 10 percent to about 400 percent of the wetting composition,more desirably from about 100 percent to about 300 percent of thewetting composition, and even more desirably from about 180 percent toabout 240 percent of the wetting composition. The wipe maintains itsdesired characteristics over the time periods involved in warehousing,transportation, retail display and storage by the consumer. Accordingly,shelf life may range from two months to two years.

Various forms of impermeable envelopes and storage means for containingwet-packaged materials, such as wipes and towelettes and the like, arewell known in the art. Any of these may be employed in packaging thepre-moistened wipes of the present invention.

Desirably, the pre-moistened wipes of the present invention are wettedwith an aqueous wetting composition, which has one or more of thefollowing properties:

(1) is compatible with the above-described triggerable bindercompositions of the present invention;

(2) enables the pre-moistened wipe to maintain its wet strength duringconverting, storage and usage (including dispensing), as well as,dispersibility in a toilet bowl;

(3) does not cause skin irritation;

(4) reduces tackiness of the wipe, and provides unique tactileproperties, such as skin glide and a “lotion-like feel”; and

(5) acts as a vehicle to deliver “moist cleansing” and other skin healthbenefits.

The wetting composition should not act as a solvent for the binder andgenerally does not contain solvents other than water, and particularlydoes not contain organic solvents, though a small quantity (<1%) of afragrance solubilizer, such as polysorbate 20, may be present, dependingon the fragrance and the salt concentration of the wetting composition.Desirably, the wetting composition contains less than about 10 weightpercent of organic solvents, such as propylene glycol or other glycols,polyhydroxy alcohols, and the like, based on the total weight of thewetting composition. More desirably, the wetting composition containsless than about 4 weight percent of organic solvents. Even moredesirably, the wetting composition contains less than about 1 weightpercent of organic solvents. The wetting composition can besubstantially free of organic solvents. By substantially free is meantcontaining only a trivial or inconsequential amount, or an amount suchthat it has no effect on the triggerable property of the product.

One aspect of the present invention is a wetting composition, whichcontains an insolubilizing agent that maintains the strength of awater-dispersable binder until the insolubilizing agent is diluted withwater, whereupon the strength of the water-dispersible binder begins todecay. The water-dispersible binder may be any of the triggerable bindercompositions of the present invention or any other triggerable bindercomposition. The insolubilizing agent in the wetting composition can bea salt, such as those disclosed for the various triggerable polymers, ablend of salts having both monovalent and multivalent ions, or any othercompound, which provides in-use and storage strength to thewater-dispersible binder composition, and can be diluted in water topermit dispersion of the substrate as the binder polymer triggers to aweaker state. Desirably, the wetting composition contains more thanabout 2 weight percent of an insolubilizing agent based on the totalweight of the wetting composition for ion-sensitive polymers and morethan about 0.5 weight percent of an insolubilizing agent based on thetotal weight of the wetting composition for ion-specific polymers.Specifically, the wetting composition may contain from about 0.5 weightpercent to about 20 weight percent of an insolubilizing agentinsolubilizing agent. Even more specifically, the wetting compositionmay contain from about 1 weight percent to about 5 weight percent of aninsolubilizing agent. More precisely, the wetting composition maycontain from about 2 weight percent to about 4 weight percent of aninsolubilizing agent. A preferred blend of salts is NaCl and ZnCl₂.

The wetting composition of the present invention may further comprise avariety of additives compatible with the insolubilizing agent and thewater-dispersible binder, such that the strength and dispersibilityfunctions of the wipe are not jeopardized. Suitable additives in thewetting composition include, but are not limited to, the followingadditives: skin-care additives; odor control agents; detackifying agentsto reduce the tackiness of the binder; particulates; antimicrobialagents; preservatives; wetting agents and cleaning agents, such asdetergents, surfactants, some silicones; emollients; surface feelmodifiers for improved tactile sensation (e.g., lubricity) on the skin;fragrance; fragrance solubilizers; opacifiers; fluorescent whiteningagents; UV absorbers; pharmaceuticals; and pH control agents, such asmalic acid or potassium hydroxide.

Skin-care Additives

As used herein, the term “skin-care additives” represents additives,which provide one or more benefits to the user, such as a reduction inthe probability of having diaper rash and/or other skin damage caused byfecal enzymes. These enzymes, particularly trypsin, chymotrypsin andelastase, are proteolytic enzymes produced in the gastrointestinal tractto digest food. In infants, for example, the feces tend to be watery andcontain, among other materials, bacteria, and some amounts of undegradeddigestive enzymes. These enzymes, if they remain in contact with theskin for any appreciable period of time, have been found to cause anirritation that is uncomfortable in itself and can predispose the skinto infection by microorganisms. As a countermeasure, skin-care additivesinclude, but are not limited to, the enzyme inhibitors and sequestrantsset forth hereafter. The wetting composition may contain less than about5 weight percent of skin-care additives based on the total weight of thewetting composition. More specifically, the wetting composition maycontain from about 0.01 weight percent to about 2 weight percent ofskin-care additives. Even more specifically, the wetting composition maycontain from about 0.01 weight percent to about 0.05 weight percent ofskin-care additives.

A variety of skin-care additives may be added to the wetting compositionand the pre-moistened wipes of the present invention or includedtherein. In one embodiment of the present invention, skin-care additivesin the form of particles are added to serve as fecal enzyme inhibitors,offering potential benefits in the reduction of diaper rash and skindamage caused by fecal enzymes. U.S. Pat. No. 6,051,749, issued Apr. 18,2000 to Schulz et al., the entirety of which is herein incorporated byreference, discloses organophilic clays in a woven or nonwoven web, saidto be useful for inhibiting fecal enzymes. Such materials may be used inthe present invention, including reaction products of a long chainorganic quaternary ammonium compound with one or more of the followingclays: montmorillonite, bentonite, beidellite, hectorite, saponite, andstevensite.

Other known enzyme inhibitors and sequestrants may be used as skin-careadditives in the wetting composition of the present invention, includingthose that inhibit trypsin and other digestive or fecal enzymes, andinhibitors for urease. For example, enzyme inhibitors and anti-microbialagents may be used to prevent the formation of odors in body fluids. Forexample, urease inhibitors, which are also said to play a role in odorabsorption, are disclosed by T. Trinh in World Patent Application No.98/26808, “Absorbent Articles with Odor Control System,” published Jun.25, 1998, the entirety of which is herein incorporated by reference.Such inhibitors may be incorporated into the wetting composition and thepre-moistened wipes of the present invention and include transitionmetal ions and their soluble salts, such as silver, copper, zinc,ferric, and aluminum salts. The anion may also provide ureaseinhibition, such as borate, phytate, etc. Compounds of potential valueinclude, but are not limited to, silver chlorate, silver nitrate,mercury acetate, mercury chloride, mercury nitrate, copper metaborate,copper bromate, copper bromide, copper chloride, copper dichromate,copper nitrate, copper salicylate, copper sulfate, zinc acetate, zincborate, zinc phytate, zinc bromate, zinc bromide, zinc chlorate, zincchloride, zinc sulfate, cadmium acetate, cadmium borate, cadmiumbromide, cadmium chlorate, cadmium chloride, cadmium formate, cadmiumiodate, cadmium iodide, cadmium permanganate, cadmium nitrate, cadmiumsulfate, and gold chloride.

Other salts that have been disclosed as having urease inhibitionproperties include ferric and aluminum salts, especially the nitrates,and bismuth salts. Other urease inhibitors are disclosed by Trinh,including hydroxamic acid and its derivatives; thiourea; hydroxylamine;salts of phytic acid; extracts of plants of various species, includingvarious tannins, e.g. carob tannin, and their derivatives such aschlorogenic acid derivatives; naturally occurring acids such as ascorbicacid, citric acid, and their salts; phenyl phosphoro diamidate/diaminophosphoric acid phenyl ester; metal aryl phosphoramidate complexes,including substituted phosphorodiamidate compounds; phosphoramidateswithout substitution on the nitrogen; boric acid and/or its salts,including especially, borax, and/or organic boron acid compounds; thecompounds disclosed in European Patent Application 408,199; sodium,copper, manganese, and/or zinc dithiocarbamate; quinones; phenols;thiurams; substituted rhodanine acetic acids; alkylated benzoquinones;formarnidine disulphide; 1:3-diketones maleic anhydride; succinamide;phthalic anhydride; pehenic acid; /N,N-dihalo-2-imidazolidinones;N-halo2-oxazolidinones; thio- and/or acyl-phosphoryltnamide and/orsubstituted derivatives thereof-, thiopyridine-N-oxides, thiopyridines,and thiopyrimidines; oxidized sulfur derivatives of diaminophosphinylcompounds; cyclotriphosphazatriene derivatives; ortho-diaminophosphinylderivatives of oximes; bromo-nitro compounds; S-aryl and/or alkyldiamidophosphorothiolates; diaminophosphinyl derivatives; mono- and/orpolyphosphorodiamide; 5-substituted-benzoxathiol-2-ones;N(diaminophosphinyl)arylcarboxamides; alkoxy-1,2-benzothaizin compounds;etc.

Many other skin-care additives may be incorporated into the wettingcomposition and pre-moistened wipes of the present invention, including,but not limited to, sun blocking agents and UV absorbers, acnetreatments, pharmaceuticals, baking soda (including encapsulated formsthereof), vitamins and their derivatives such as Vitamins A or E,botanicals such as witch hazel extract and aloe vera, allantoin,emollients, disinfectants, hydroxy acids for wrinkle control oranti-aging effects, sunscreens, tanning promoters, skin lighteners,deodorants and antiperspirants, ceramides for skin benefits and otheruses, astringents, moisturizers, nail polish removers, insectrepellants, antioxidants, antiseptics, anti-inflammatory agents and thelike, provided that the additives are compatible with an ion-sensitivebinder composition associated therewith, and especially theion-sensitive binder compositions of the present invention (i.e., theydo not cause a substantial loss of strength in the wet state of thepre-moistened wipes, prior to dilution in water, while permittingdispersibility in water).

Useful materials for skin care and other benefits are listed inMcCutcheon's 1999, Vol. 2: Functional Materials, MC Publishing Company,Glen Rock, N.J. Many useful botanicals for skin care are provided byActive Organics, Lewisville, Tex.

Odor Control Additives

Suitable odor control additives for use in the wetting composition andpre-moistened wipes of the present invention include, but are notlimited to, zinc salts; talc powder; encapsulated perfumes (includingmicrocapsules, macrocapsules, and perfume encapsulated in liposomes,vessicles, or microemulsions); chelants, such as ethylenediaminetetra-acetic acid; zeolites; activated silica, activated carbon granulesor fibers; activated silica particulates; polycarboxylic acids, such ascitric acid; cyclodextrins and cyclodextrin derivatives; chitosan orchitin and derivatives thereof; oxidizing agents; antimicrobial agents,including silver-loaded zeolites (e.g., those of BF Technologies,located in Beverly, Mass., sold under the trademark HEALTHSHIELD™);triclosan; kieselguhr; and mixtures thereof. In addition to controllingodor from the body or body wastes, odor control strategies can also beemployed to mask or control any odor of the treated substrate.Desirably, the wetting composition contains less than about 5 weightpercent of odor control additives based on the total weight of thewetting composition. More desirably, the wetting composition containsfrom about 0.01 weight percent to about 2 weight percent of odor controladditives. Even more desirably, the wetting composition contains fromabout 0.03 weight percent to about 1 weight percent of odor controladditives.

In one embodiment of the present invention, the wetting compositionand/or pre-moistened wipes comprise derivatized cyclodextrins, such ashydroxypropyl beta-cyclodextrin in solution, which remain on the skinafter wiping and provide an odor-absorbing layer. In other embodiments,the odor source is removed or neutralized by application of anodor-control additive, exemplified by the action of a chelant that bindsmetal groups necessary for the function of many proteases and otherenzymes that commonly produce an odor. Chelating the metal groupinterferes with the enzyme's action and decreases the risk of malodor inthe product.

Principles for the application of chitosan or chitin derivatives tononwoven webs and cellulosic fibers are described by S. Lee et al. in“Antimicrobial and Blood Repellent Finishes for Cotton and NonwovenFabrics Based on Chitosan and Fluoropolymers,” Textile Research Journal,69(2); 104-112, February 1999.

Detackifying Agents

While elevated salt concentrations may reduce the tack of thetriggerable binder, other means of tack reduction are often desirable.Thus, detackifying agents may be used in the wetting composition toreduce the tackiness, if any, of the triggerable binder. Suitabledetackifiers include any substance known in the art to reduce tackbetween two adjacent fibrous sheets treated with an adhesive-likepolymer or any substance capable of reducing the tacky feel of anadhesive-like polymer on the skin. Detackifiers may be applied as solidparticles in dry form, as a suspension or as a slurry of particles.Deposition may be by spray, coating, electrostatic deposition,impingement, filtration (i.e., a pressure differential drives aparticle-laden gas phase through the substrate, depositing particles bya filtration mechanism), and the like, and may be applied uniformly onone or more surfaces of the substrate or may be applied in a pattern(e.g., repeating or random patterns) over a portion of the surface orsurfaces of the substrate. The detackifier may be present throughout thethickness of the substrate, but may be concentrated at one or bothsurfaces, and may be substantially only present on one or both surfacesof the substrate.

Specific detackifiers include, but are not limited to, powders, such astalc powder, calcium carbonate, mica; starches, such as corn starch;lycopodium powder; mineral fillers, such as titanium dioxide; silicapowder; alumina; metal oxides in general; baking powder; kieselguhr; andthe like. Polymers and other additives having low surface energy mayalso be used, including a wide variety of fluorinated polymers, siliconeadditives, polyolefins and thermoplastics, waxes, debonding agents knownin the paper industry including compounds having alkyl side chains suchas those having 16 or more carbons, and the like. Compounds used asrelease agents for molds and candle making may also be considered, aswell as, dry lubricants and fluorinated release agents.

In one embodiment, the detackifier comprises polytetrafluorethylene(PTFE), such as PTFE telomer (KRYTOX® DF) compound, used in the PTFErelease agent dry lubricant MS-122DF, marketed by Miller-Stephenson(Danbury, Conn.) as a spray product. For example, PTFE particles may beapplied by spray to one side of the substrate prior to winding of thepre-moistened wipes. In one embodiment, a detackifying agent is appliedto only one surface of the substrate prior to winding into a roll.

The wetting composition desirably contains less than about 25 weightpercent of detackifying agents based on the total weight of the wettingcomposition. More desirably, the wetting composition contains from about0.01 weight percent to about 10 weight percent of detackifying agents,more specifically about 5% or less. Even more specifically, the wettingcomposition contains from about 0.05 weight percent to about 2 weightpercent of detackifying agents.

In addition to acting as a detackifying agent, starch compounds may alsoimprove the strength properties of the pre-moistened wipes. For example,it has been found that ungelled starch particles, such as hydrophilictapioca starch, when present at a level of about 1% or higher by weightrelative to the weight of the wetting composition, can permit thepre-moistened wipe to maintain the same strength at a lower saltconcentration than is possible without the presence of starch. Thus, forexample, a given strength can be achieved with 2% salt in the wettingcomposition in the presence of salt compared to a level of 4% salt beingneeded without starch. Starch may be applied by adding the starch to asuspension of laponite to improve the dispersion of the starch withinthe wetting composition.

Microparticulates

The wetting composition of the present invention may be further modifiedby the addition of solid particulates or microparticulates. Suitableparticulates include, but are not limited to, mica, silica, alumina,calcium carbonate, kaolin, talc, and zeolites. The particulates may betreated with stearic acid or other additives to enhance the attractionor bridging of the particulates to the binder system, if desired. Also,two-component microparticulate systems, commonly used as retention aidsin the papermaking industry, may also be used. Such two-componentmicroparticulate systems generally comprise a colloidal particle phase,such as silica particles, and a water-soluble cationic polymer forbridging the particles to the fibers of the web to be formed. Thepresence of particulates in the wetting composition can serve one ormore useful functions, such as (1) increasing the opacity of thepre-moistened wipes; (2) modifying the rheology or reducing thetackiness of the pre-moistened wipe; (3) improving the tactileproperties of the wipe; or (4) delivering desired agents to the skin viaa particulate carrier, such as a porous carrier or a microcapsule.Desirably, the wetting composition contains less than about 25 weightpercent of particulate based on the total weight of the wettingcomposition. More specifically, the wetting composition may contain fromabout 0.05 weight percent to about 10 weight percent ofmicroparticulate. Even more specifically, the wetting composition maycontain from about 0.1 weight percent to about 5 weight percent ofmicroparticulate.

Microcapsules and other Delivery Vehicles

Microcapsules and other delivery vehicles may also be used in thewetting composition of the present invention to provide skin-careagents; medications; comfort promoting agents, such as eucalyptus;perfumes; skin care agents; odor control additives; vitamins; powders;and other additives to the skin of the user. Specifically, the wettingcomposition may contain up to about 25 weight percent of microcapsulesor other delivery vehicles based on the total weight of the wettingcomposition. More specifically, the wetting composition may contain fromabout 0.05 weight percent to about 10 weight percent of microcapsules orother delivery vehicles. Even more specifically, the wetting compositionmay contain from about 0.2 weight percent to about 5.0 weight percent ofmicrocapsules or other delivery vehicles.

Microcapsules and other delivery vehicles are well known in the art. Forexample, POLY-PORE® E200 (Chemdal Corp., Arlington Heights, Ill.), is adelivery agent comprising soft, hollow spheres that can contain anadditive at over 10 times the weight of the delivery vehicle. Knownadditives reported to have been used with POLY-PORE® E200 include, butare not limited to, benzoyl peroxide, salicylic acid, retinol, retinylpalmitate, octyl methoxycinnamate, tocopherol, silicone compounds (DC435), and mineral oil. Another useful delivery vehicle is a sponge-likematerial marketed as POLY-PORE® L200, which is reported to have beenused with silicone (DC 435) and mineral oil. Other known deliverysystems include cyclodextrins and their derivatives, liposomes,polymeric sponges, and spray-dried starch.

Additives present in microcapsules are isolated from the environment andthe other agents in the wetting composition until the wipe is applied tothe skin, whereupon the microcapsules break and deliver their load tothe skin or other surfaces.

Preservatives and Anti-Microbial Agents

The wetting composition of the present invention may also containpreservatives and/or anti-microbial agents. Several preservatives and/oranti-microbial agents, such as Mackstat H 66 (available from McIntyreGroup, Chicago, Ill., have been found to give excellent results inpreventing bacteria and mold growth. Other suitable preservatives andanti-microbial agents include, but are not limited to DMDM hydantoin(e.g., Glydant Plus™, Lonza, Inc., Fair Lawn, N.J.), iodopropynylbutylcarbamate, Kathon (Rohm and Hass, Philadelphia, Pa.),methylparaben, propylparaben, 2-bromo-2-nitropropane-1,3-diol, benzoicacid, and the like. Desirably, the wetting composition contains lessthan about 2 weight percent on an active basis of preservatives and/oranti-microbial agents based on the total weight of the wettingcomposition. More desirably, the wetting composition contains from about0.01 weight percent to about 1 weight percent of preservatives and/oranti-microbial agents. Even more desirably, the wetting compositioncontains from about 0.01 weight percent to about 0.5 weight percent ofpreservatives and/or anti-microbial agents.

Wetting Agents and Cleaning Agents

A variety of wetting agents and/or cleaning agents may be used in thewetting composition of the present invention. Suitable wetting agentsand/or cleaning agents include, but are not limited to, detergents andnonionic, amphoteric, and anionic surfactants, especially aminoacid-based surfactants. Amino acid-based surfactant systems, such asthose derived from amino acids L-glutamic acid and other natural fattyacids, offer pH compatibility to human skin and good cleansing power,while being relatively safe and providing improved tactile andmoisturization properties compared to other anionic surfactants. Onefunction of the surfactant is to improve wetting of the dry substratewith the wetting composition. Another function of the surfactant can beto disperse bathroom soils when the pre-moistened wipe contacts a soiledarea and to enhance their absorption into the substrate. The surfactantcan farther assist in make-up removal, general personal cleansing, hardsurface cleansing, odor control, and the like.

One commercial example of an amino-acid based surfactant isacylglutamate, marketed under the Amisoft name by Ajinomoto Corp.,Tokyo, Japan. Desirably, the wetting composition contains less thanabout 3 weight percent of wetting agents and/or cleaning agents based onthe total weight of the wetting composition. More desirably, the wettingcomposition contains from about 0.01 weight percent to about 2 weightpercent of wetting agents and/or cleaning agents. Even more desirably,the wetting composition contains from about 0.1 weight percent to about0.5 weight percent of wetting agents and/or cleaning agents.

Although amino-acid based surfactants are particularly useful in thewetting compositions of the present invention, a wide variety ofsurfactants may be used in the present invention. Suitable non-ionicsurfactants include, but are not limited to, the condensation productsof ethylene oxide with a hydrophobic (oleophilic) polyoxyalkylene baseformed by the condensation of propylene oxide with propylene glycol. Thehydrophobic portion of these compounds desirably has a molecular weightsufficiently high so as to render it water-insoluble. The addition ofpolyoxyethylene moieties to this hydrophobic portion increases thewater-solubility of the molecule as a whole, and the liquid character ofthe product is retained up to the point where the polyoxyethylenecontent is about 50% of the total weight of the condensation product.Examples of compounds of this type include commercially-availablePluronic surfactants (BASF Wyandotte Corp.), especially those in whichthe polyoxypropylene ether has a molecular weight of about 1500-3000 andthe polyoxyethylene content is about 35-55% of the molecule by weight,i.e. Pluronic L-62.

Other useful nonionic surfactants include, but are not limited to, thecondensation products of C₈-C₂₂ alkyl alcohols with 2-50 moles ofethylene oxide per mole of alcohol. Examples of compounds of this typeinclude the condensation products of C₁₁-C₁₅ secondary alkyl alcoholswith 3-50 moles of ethylene oxide per mole of alcohol, which arecommercially-available as the Poly-Tergent SLF series from OlinChemicals or the TERGITOL® series from Union Carbide; i.e., TERGITOL®25-L-7, which is formed by condensing about 7 moles of ethylene oxidewith a C₁₂-C₁₅ alkanol.

Other nonionic surfactants, which may be employed in the wettingcomposition of the present invention, include the ethylene oxide estersof C₆-C₁₂ alkyl phenols such as (nonylphenoxy)polyoxyethylene ether.Particularly useful are the esters prepared by condensing about 8-12moles of ethylene oxide with nonylphenol, i.e. the IGEPAL® CO series(GAF Corp.).

Further non-ionic surface active agents include, but are not limited to,alkyl polyglycosides (APG), derived as a condensation product ofdextrose (D-glucose) and a straight or branched chain alcohol. Theglycoside portion of the surfactant provides a hydrophile having highhydroxyl density, which enhances water solubility. Additionally, theinherent stability of the acetal linkage of the glycoside provideschemical stability in alkaline systems. Furthermore, unlike somenon-ionic surface active agents, alkyl polyglycosides have no cloudpoint, allowing one to formulate without a hydrotrope, and these arevery mild, as well as readily biodegradable non-ionic surfactants. Thisclass of surfactants is available from Horizon Chemical under the tradenames of APG-300, APG-350, APG-500, and APG-500.

Silicones are another class of wetting agents available in pure form, oras microemulsions, macroemulsions, and the like. One exemplary non-ionicsurfactant group is the silicone-glycol copolymers. These surfactantsare prepared by adding poly(lower)alkylenoxy chains to the free hydroxylgroups of dimethylpolysiloxanols and are available from the Dow ComingCorp as Dow Coming 190 and 193 surfactants (CTFA name: dimethiconecopolyol). These surfactants function, with or without any volatilesilicones used as solvents, to control foaming produced by the othersurfactants, and also impart a shine to metallic, ceramic, and glasssurfaces.

Anionic surfactants may also be used in the wetting compositions of thepresent invention. Anionic surfactants are useful due to their highdetergency include anionic detergent salts having alkyl substituents of8 to 22 carbon atoms such as the water-soluble higher fatty acid alkalimetal soaps, e.g., sodium myristate and sodium palmitate. A preferredclass of anionic surfactants encompasses the water-soluble sulfated andsulfonated anionic alkali metal and alkaline earth metal detergent saltscontaining a hydrophobic higher alkyl moiety (typically containing fromabout 8 to 22 carbon atoms) such as salts of higher alkyl mono orpolynuclear aryl sulfonates having from about 1 to 16 carbon atoms inthe alkyl group, with examples available as the Bio-Soft series, i.e.Bio-Soft D-40 (Stepan Chemical Co.).

Other useful classes of anionic surfactants include, but are not limitedto, the alkali metal salts of alkyl naphthalene sulfonic acids (methylnaphthalene sodium sulfonate, Petro AA, Petrochemical Corporation);sulfated higher fatty acid monoglycerides such as the sodium salt of thesulfated monoglyceride of cocoa oil fatty acids and the potassium saltof the sulfated monoglyceride of tallow fatty acids; alkali metal saltsof sulfated fatty alcohols containing from about 10 to 18 carbon atoms(e.g., sodium lauryl sulfate and sodium stearyl sulfate); sodiumC₁₄-C₁₆-alphaolefin sulfonates such as the Bio-Terge series (StepanChemical Co.); alkali metal salts of sulfated ethyleneoxy fatty alcohols(the sodium or ammonium sulfates of the condensation products of about 3moles of ethylene oxide with a C₁₂-C₁₅ n-alkanol; i.e., the Neodolethoxysulfates, Shell Chemical Co.); alkali metal salts of higher fattyesters of low molecular weight alkylol sulfonic acids, e.g. fatty acidesters of the sodium salt of isothionic acid, the fatty ethanolamidesulfates; the fatty acid amides of amino alkyl sulfonic acids; e.g.,lauric acid amide of taurine; as well as numerous other anionic organicsurface active agents such as sodium xylene sulfonate, sodiumnaphthalene sulfonate, sodium toulene sulfonate and mixtures thereof.

A further useful class of anionic surfactants includes the8-(4-n-alkyl-2-cyclohexenyl)-octanoic acids, wherein the cyclohexenylring is substituted with an additional carboxylic acid group. Thesecompounds or their potassium salts, are commercially-available fromWestvaco Corporation as Diacid 1550 or H-240. In general, these anionicsurface active agents can be employed in the form of their alkali metalsalts, ammonium or alkaline earth metal salts.

Macroemulsions and Microemulsion of Silicone Particles

The wetting composition may further comprise an aqueous microemulsion ofsilicone particles. For example, U.S. Pat. No. 6,037,407, “Process forthe Preparation of Aqueous Emulsions of Silicone Oils and/or Gums and/orResins” issued Mar. 14, 2000, discloses organopolysiloxanes in anaqueous microemulsion. Desirably, the wetting composition contains lessthan about 5 weight percent of a microemulsion of silicone particlesbased on the total weight of the wetting composition. More desirably,the wetting composition contains from about 0.02 weight percent to about3 weight percent of a microemulsion of silicone particles. Even moredesirably, the wetting composition contains from about 0.02 weightpercent to about 0.5 weight percent of a microemulsion of siliconeparticles.

Silicone emulsions in general may be applied to the pre-moistened wipeby any known coating method. For example, the pre-moistened wipe may bemoistened with an aqueous composition comprising a water-dispersible orwater-miscible, silicone-based component that is compatible with theinsolubilizing compound in the wetting composition. Further, the wipecan comprise a nonwoven web of fibers having a water-dispersible binder,wherein the web is moistened with a lotion comprising a silicone-basedsulfosuccinate. The silicone-based sulfosuccinate provides gentle andeffective cleansing without a high level of surfactant. Additionally,the silicone-based sulfosuccinate provides a solubilization function,which prevents precipitation of oil-soluble components, such asfragrance components, vitamin extracts, plant extracts, and essentialoils.

In one embodiment of the present invention, the wetting compositioncomprises a silicone copolyol sulfosuccinate, such as disodiumdimethicone copolyol sulfosuccinate and diammonium dimethiconecopolyolsulfosuccinate. Desirably, the wetting composition comprisesless than about 2 percent by weight of the silicone-basedsulfosuccinate, and more desirably from about 0.05 percent to about 0.30percent by weight of the silicone-based sulfosuccinate.

In another example of a product comprising a silicone emulsions, DowCorning 9506 powder may also be present in the wetting composition. DowCorning 9506 powder is believed to comprise adimethicone/vinyldimethicone cross-polymer and is a spherical powder,which is said to be useful in controlling skin oils (see “New ChemicalPerspectives,” Soap and Cosmetics, Vol. 76, No. 3, March 2000, p. 12).Thus, a water-dispersible wipe, which delivers a powder effective incontrolling skin oil, is also within the scope of the present invention.Principles for preparing silicone emulsions are disclosed in WO97/10100, published Mar. 20, 1997.

Emollients

The wetting composition of the present invention may also contain one ormore emollients. Suitable emollients include, but are not limited to,PEG 75 lanolin, methyl gluceth 20 benzoate, C₁₂-C₁₅ alkyl benzoate,ethoxylated cetyl stearyl alcohol, products marketed as Lambent waxWS—L, Lambent WD—F, Cetiol HE (Henkel Corp.), Glucam P20 (Amerchol),Polyox WSR N-10 (Union Carbide), Polyox WSR N-3000 (Union Carbide),Luviquat (BASF), Finsolv SLB 101 (Finetex Corp.), mink oil, allantoin,stearyl alcohol, Estol 1517 (Unichema), and Finsolv SLB 201 (FinetexCorp.).

An emollient can also be applied to a surface of the article prior to orafter wetting with the wetting composition. Such an emollient may beinsoluble in the wetting composition and can be immobile except whenexposed to a force. For example, a petrolatum-based emollient can beapplied to one surface in a pattern, after which the other surface iswetted to saturate the wipe. Such a product could provide a cleaningsurface and an opposing skin treatment surface.

The emollient composition in such products and other products of thepresent invention can comprise a plastic or fluid emollient such as oneor more liquid hydrocarbons (e.g., petrolatum), mineral oil and thelike, vegetable and animal fats (e.g., lanolin, phospholipids and theirderivatives) and/or a silicone materials such as one or more alkylsubstituted polysiloxane polymers, including the polysiloxane emollientsdisclosed in U.S. Pat. No. 5,891,126, issued Apr. 6, 1999 to Osborn, IIIet al. Optionally, a hydrophilic surfactant may be combined with aplastic emollient to improve wettability of the coated surface. In someembodiments of the present invention, it is contemplated that liquidhydrocarbon emollients and/or alkyl substituted polysiloxane polymersmay be blended or combined with one or more fatty acid ester emollientsderived from fatty acids or fatty alcohols.

In an embodiment of the present invention, the emollient material is inthe form of an emollient blend. Desirably, the emollient blend comprisesa combination of one or more liquid hydrocarbons (e.g., petrolatum),mineral oil and the like, vegetable and animal fats (e.g., lanolin,phospholipids and their derivatives), with a silicone material such asone or more alkyl substituted polysiloxane polymers. More desirably, theemollient blend comprises a combination of liquid hydrocarbons (e.g.,petrolatum) with dimethicone or with dimethicone and other alkylsubstituted polysiloxane polymers. In some embodiments of the presentinvention, it is contemplated that blends of liquid hydrocarbonemollients and/or alkyl substituted polysiloxane polymers may be blendedwith one or more fatty acid ester emollients derived from fatty acids orfatty alcohols. PEG-7 glyceryl cocoate, available as Standamul HE(Henkel Corp., Hoboken, N.J.), can also be considered.

Water-soluble, self-emulsifying emollient oils, which are useful in thepresent wetting compositions, include the polyoxyalkoxylated lanolinsand the polyoxyalkoxylated fatty alcohols, as disclosed in U.S. Pat. No.4,690,821, issued Sep. 1, 1987 to Smith et al. The polyoxyalkoxy chainsdesirably will comprise mixed propylenoxy and ethyleneoxy units. Thelanolin derivatives will typically comprise about 20-70 suchlower-alkoxy units while the C₁₂-C₂₀-fatty alcohols will be derivatizedwith about 8-15 lower-alkyl units. One such useful lanolin derivative isLanexol AWS (PPG-12-PEG-50, Croda, Inc., New York, N.Y.). A usefulpoly(15-20)C₂-C₃-alkoxylate is PPG-5-Ceteth-20, known as Procetyl AWS(Croda, Inc.).

According to one embodiment of the present invention, the emollientmaterial reduces undesirable tactile attributes, if any, of the wettingcomposition. For example, emollient materials, including dimethicone,can reduce the level of tackiness that may be caused by theion-sensitive binder or other components in the wetting composition,thus serving as a detackifier.

Desirably, the wetting composition contains less than about 25 weightpercent of emollients based on the total weight of the wettingcomposition. More specifically, the wetting composition may compriseless than about 5 weight percent emollient, and most specifically lessthan about 2% emollient. More desirably, the wetting composition maycontain from about 0.01 weight percent to about 8 weight percent ofemollients. Even more desirably, the wetting composition may containfrom about 0.2 weight percent to about 2 weight percent of emollients.

In one embodiment, the wetting composition and/or pre-moistened wipes ofthe present invention comprise an oil-in-water emulsion comprising anoil phase containing at least one emollient oil and at least oneemollient wax stabilizer dispersed in an aqueous phase comprising atleast one polyhydric alcohol emollient and at least one organicwater-soluble detergent, as disclosed in U.S. Pat. No. 4,559,157, issuedDec. 17, 1985 to Smith et al., the entirety of which is hereinincorporated by reference.

Surface Feel Modifiers

Surface feel modifiers are used to improve the tactile sensation (e.g.,lubricity) of the skin during use of the product. Suitable surface feelmodifiers include, but are not limited to, commercial debonders; andsofteners, such as the softeners used in the art of tissue makingincluding quaternary ammonium compounds with fatty acid side groups,silicones, waxes, and the like. Exemplary quaternary ammonium compoundswith utility as softeners are disclosed in U.S. Pat. No. 3,554,862,issued to Hervey et al. on Jan. 12, 1971; U.S. Pat. No. 4,144,122,issued to Emanuelsson et al., Mar. 13, 1979, U.S. Pat. No. 5,573,637,issued to Ampulski et al. Nov. 12, 1996; and U.S. Pat. No. 4,476,323,issued to Hellsten et al., Oct. 9, 1984, the entirety of all of which isherein incorporated by reference. Desirably, the wetting compositioncontains less than about 2 weight percent of surface feel modifiersbased on the total weight of the wetting composition. More desirably,the wetting composition contains from about 0.01 weight percent to about1 weight percent of surface feel modifiers. Even more desirably, thewetting composition contains from about 0.01 weight percent to about0.05 weight percent of surface feel modifiers.

Fragrances

A variety of fragrances may be used in the wetting composition of thepresent invention. Desirably, the wetting composition contains less thanabout 2 weight percent of fragrances based on the total weight of thewetting composition. More desirably, the wetting composition containsfrom about 0.01 weight percent to about 1 weight percent of fragrances.Even more desirably, the wetting composition contains from about 0.01weight percent to about 0.05 weight percent of fragrances.

Fragrance Solubilizers

Further, a variety of fragrance solubilizers may be used in the wettingcomposition of the present invention. Suitable fragrance solubilizersinclude, but are not limited to, polysorbate 20, propylene glycol,ethanol, isopropanol, diethylene glycol monoethyl ether, dipropyleneglycol, diethyl phthalate, triethyl citrate, Ameroxol OE-2 (AmercholCorp.), Brij 78 and Brij 98 (ICI Surfactants), Arlasolve 200 (ICISurfactants), Calfax 16L-35 (Pilot Chemical Co.), Capmul POE-S (AbitecCorp.), Finsolv SUBSTANTIAL (Finetex), and the like. Desirably, thewetting composition contains less than about 2 weight percent offragrance solubilizers based on the total weight of the wettingcomposition. More desirably, the wetting composition contains from about0.01 weight percent to about 1 weight percent of fragrance solubilizers.Even more desirably, the wetting composition contains from about 0.01weight percent to about 0.05 weight percent of fragrance solubilizers.

Opacifiers

Suitable opacifiers include, but are not limited to, titanium dioxide orother minerals or pigments, and synthetic opacifiers, such asREACTOPAQUE® particles (available from Sequa Chemicals, Inc., Chester,S.C.). Desirably, the wetting composition contains less than about 2weight percent of opacifiers based on the total weight of the wettingcomposition. More desirably, the wetting composition contains from about0.01 weight percent to about 1 weight percent of opacifiers. Even moredesirably, the wetting composition contains from about 0.01 weightpercent to about 0.05 weight percent of opacifiers.

pH Control Agents

Suitable pH control agents for use in the wetting composition of thepresent invention include, but are not limited to, hydrochloric acid,acetic acid, sodium hydroxide, potassium hydroxide, and the like. Anappropriate pH range minimizes the amount of skin irritation resultingfrom the wetting composition on the skin. Desirably, the pH range of thewetting composition is from about 3.5 to about 6.5. More desirably, thepH range of the wetting composition is from about 4 to about 6.Desirably the overall pH of the wet wipe product; i.e., the complete wetwipe product including the fabric portion and the wetting solutionportion, is from about 3.9-4.5; preferably, about 4.2. Desirably, thewetting composition contains less than about 2 weight percent of a pHadjuster based on the total weight of the wetting composition. Moredesirably, the wetting composition contains from about 0.01 weightpercent to about 1 weight percent of a pH adjuster. Even more desirably,the wetting composition contains from about 0.01 weight percent to about0.05 weight percent of a pH adjuster.

Although a variety of wetting compositions, formed from one or more ofthe above-described components, may be used with the wet wipes of thepresent invention, in one embodiment, the wetting composition containsthe following components, given in weight percent of the wettingcomposition, as shown in Table 2 below:

TABLE 2 Wetting Composition Components Wetting Composition Component:Weight Percent: Deionized Water about 86 to about 98 Insolubilizingcompound about 2 to about 20 Preservative Up to about 2 Surfactant Up toabout 2 Silicone Emulsion Up to about 1 Emollient Up to about 1Fragrance Up to about 0.3 Fragrance solubilizer Up to about 0.5 pHadjuster Up to about 0.2

In another embodiment of the present invention, the wetting compositioncomprises the following components, given in weight percent of thewetting composition, as shown in Table 3 below:

TABLE 3 Wetting Composition Components Class of Wetting Specific WettingComposition Composition Component Weight Component: Component: Name:Percent: Vehicle Deionized Water about 86 to about 98 InsolubilizingSodium Chloride about 2 to compound (Millport Ent., about 20 Milwaukee,WI) Preservative Glycerin, IPBC and Mackstat H-66 Up to about 2 DMDMHydantoin (McIntyre Group, Chicago, IL) Surfactant Acyl Glutamate CS22Up to about 2 (Ajinomoto, Tokyo, Japan) Silicone Dimethiconol and DC1785Up to about 1 Emulsion TEA (Dow Corning, (Detackifier/Sk DodecylbenezeneMidland, MI) in Feel agent) Sulfonate Emollient PEG-75 Lanolin SolulanL- 575 Up to about 1 (Amerchol, Middlesex, NJ) Fragrance FragranceDragoco Up to about 0.3 0/708768 (Dragoco, Roseville, MN) FragrancePolysorbate 20 Glennsurf L20 Up to about 0.5 solubilizer (Glenn Corp.,St. Paul, MN) pH adjuster Malic Acid to pH 5 Up to about 0.2 (Haarman &Reimer, Tetrboro, NJ)

In another embodiment of the present invention, the wetting compositioncomprises the following components, given in weight percent of thewetting composition, as shown in Table 4 below:

TABLE 4 An Exemplary Wetting Composition Class of Specific WettingWetting composition composition Component Weight Component: Component:Name: Percent: Vehicle Deionized Water about 93 Insolubilizing ZincChloride about 1 compound Preservative Glycerin, IPBC and Mackstat about1 DMDM Hydantoin H-66 Surfactant Acyl Glutamate CS22/ECS about 1 22PSilicone Dimethiconol and DC 1784/ about 0.5 Emulsion TEA DC1785Dodecylbenezene Sulfonate Emollient PEG-75 Lanolin Solulan L- 575 about0.25 Fragrance Fragrance Dragoco about 0.05 Fragrance 0/708768 FragrancePolysorbate 20 Glennsurf L20 about 0.25 solubilizer pH adjuster MalicAcid to pH 5 about 0.07

It should be noted that the above-described wetting compositions of thepresent invention may be used with any one of the above-describedtriggerable binder compositions of the present invention. Further, theabove-described wetting compositions of the present invention may beused with any other binder composition, including conventional bindercompositions, or with any known fibrous or absorbent substrate, whetherdispersible or not.

Strength Properties

In one embodiment of the present invention, wet wipes are produced usingthe above-described wetting composition in Table 3 and an air-laidfibrous material comprising about 80 weight percent of bleached kraftfibers and 20 weight percent of any of the above-described ion-specificbinder compositions of the present invention, wherein the weightpercentages are based on the total weight of the dry nonwoven fabric. Ina further embodiment of the present invention, wet wipes are producedusing the above-described wetting composition in Table 2 and an air-laidfibrous material comprising 90 weight percent of softwood fibers and 10weight percent of an ion-sensitive binder of the present invention. Theamount of wetting composition added to the nonwoven fabric, relative tothe weight of the dry nonwoven fabric in these embodiments, is desirablyabout 180 percent to about 240 weight percent.

Desirably, the wet wipes of the present invention possess an in-use wettensile strength cross deckle wet tensile (CDWT) of at least about 100g/in, and a tensile strength of less than about 30 g/in after beingsoaked in water having a concentration of Ca²⁺ and/or Mg²⁺ ions of about50 ppm for about one hour. More desirably, the wet wipes possess anin-use wet tensile strength of at least about 300 g/in (CDWT), and atensile strength of less than about 20 g/in after being soaked in waterhaving a concentration of Ca²⁺ and/or Mg²⁺ ions of about 50 ppm forabout one hour. In a further embodiment, the wet wipes desirably possessan in-use wet tensile strength of at least about 100 g/in (CDWT), and atensile strength of less than about 30 g/in after being soaked in waterhaving a concentration of Ca ²⁺ and/or Mg²⁺ ions of about 200 ppm forabout one hour. Even more desirably, the wet wipes possess an in-use wettensile strength of at least about 300 g/in (CDWT), and a tensilestrength of less than about 20 g/in after being soaked in water having aconcentration of Ca²⁺ and/or Mg²⁺ ions of about 200 ppm for about onehour.

Desirably, the wet wipes treated with the binder material of the presentinvention possess an in-use wet tensile strength of at least 100 g/infor a 1 inch width sample in the cross machine direction when soakedwith 10% to 400% by weight wet wipes solution containing more than 2% byweight monovalent ion (NaCl) concentration and a tensile strength ofless than about 30 g/in after being soaked in deionized water for aboutone hour. More desirably, the wet wipes treated with the binder materialof the present invention possess an in-use tensile strength of at least200 g/in for a 1 inch width sample in the cross machine direction whensoaked with 10% to 400% by weight wet wipes solution containing morethan 2% by weight monovalent ion (NaCl) concentration and a tensilestrength of less than about 30 g/in after being soaked in deionizedwater for about one hour. More desirably, the wet wipes treated with thebinder material of the present invention possess an in-use tensilestrength of at least 300 g/in for a 1 inch width sample in the crossmachine direction when soaked with 10% to 400% by weight wet wipessolution containing more than 2% by weight monovalent ion (NaCl)concentration and a tensile strength of less than about 20 g/in afterbeing soaked in deionized water for about one hour.

Desirably, the wet wipes treated with the binder material of the presentinvention possess an in-use wet tensile strength of at least 100 g/infor a 1 inch width sample in the cross machine direction when soakedwith 10% to 400% by weight wet wipes solution containing more than 0.5%by weight ZnCl₂ and a tensile strength of less than about 30 g/in afterbeing soaked in deionized water for about one hour. More desirably, thewet wipes treated with the binder material of the present inventionpossess an in-use tensile strength of at least 200 g/in for a 1 inchwidth sample in the cross machine direction when soaked with 10% to 400%by weight wet wipes solution containing more than 0.5% by weight ZnCl₂and a tensile strength of less than about 30 g/in after being soaked indeionized water for about one hour. More desirably, the wet wipestreated with the binder material of the present invention possess anin-use tensile strength of at least 300 g/in for a 1 inch width samplein the cross machine direction when soaked with 10% to 400% by weightwet wipes solution containing more than 0.5% by weight ZnCl₂ and atensile strength of less than about 20 g/in after being soaked indeionized water for about one hour.

Products with high basis weights or wet strengths than flushable wetwipes may have relatively higher wet tensile strength. For example,products, such as pre-moistened towels or hard-surface cleaning wipes,may have basis weights above 70 gsm, such as from 80 gsm to 150 gsm.Such products can have CDWT values of 500 g/in or greater, and aftersoaking values of about 150 g/in or less, more specifically about 100g/in or less, and most specifically about 50 g/in or less.

Method of Making Wet Wipes

The pre-moistened wipes of the present invention can be made in severalways. In one embodiment, the triggerable polymer composition is appliedto a fibrous substrate as part of an aqueous solution or suspension,wherein subsequent drying is needed to remove the water and promotebinding of the fibers. In particular, during drying, the binder migratesto the crossover points of the fibers and becomes activated as a binderin those regions, thus providing acceptable strength to the substrate.For example, the following steps can be applied:

1. Providing an absorbent substrate that is not highly bonded (e.g., anunbonded airlaid, a tissue web, a carded web, fluff pulp, etc.).

2. Applying a triggerable polymer composition to the substrate,typically in the form of a liquid, suspension, or foam.

3. Drying the substrate to promote bonding of the substrate. Thesubstrate may be dried such that the peak substrate temperature does notexceed about 100° to 220° C. In one embodiment, the substratetemperature does not exceed 60° C. to 80° C.

5. Applying a wetting composition to the substrate.

6. Placing the wetted substrate in roll form or in a stack and packagingthe product.

Application of the triggerable polymer composition to the substrate canbe by means of spray; by foam application; by immersion in a bath; bycurtain coating; by coating and metering with a wire-wound rod; bypassage of the substrate through a flooded nip; by contact with apre-metered wetted roll coated with the binder solution; by pressing thesubstrate against a deformable carrier containing the triggerablepolymer composition such as a sponge or felt to effect transfer into thesubstrate; by printing such as gravure, inkjet, or flexographicprinting; and any other means known in the art.

In the use of foams to apply a binder or co-binder polymer, the mixtureis frothed, typically with a foaming agent, and spread uniformly on thesubstrate, after which vacuum is applied to pull the froth through thesubstrate. Any known foam application method can be used, including thatof U.S. Pat. No. 4,018,647, “Process for the Impregnation of a Wet FiberWeb with a Heat Sensitized Foamed Latex Binder,” issued Apr. 19, 1977 toWietsma, the entirety of which is herein incorporated by reference.Wietsma discloses a method wherein a foamed latex is heat-sensitized bythe addition of a heat-sensitizer such as functional siloxane compoundsincluding siloxane oxyalkylene block copolymers and organopolysiloxanes.Specific examples of applicable heat-sensitizers and their use thereoffor the heat sensitization of latices are described in the U.S. Pat.Nos. 3,255,140; 3,255,141; 3,483,240 and 3,484,394, all of which areincorporated herein by reference. The use of a heat-sensitizer is saidto result in a product having a very soft and textile-like hand comparedto prior methods of applying foamed latex binders.

The amount of heat-sensitizer to be added is dependent on, inter alia,the type of latex used, the desired coagulation temperature, the machinespeed and the temperatures in the drying section of the machine, andwill generally be in the range of about 0.05 to about 3% by weight,calculated as dry matter on the dry weight of the latex; but also largeror smaller amounts may be used. The heat sensitizer can be added in suchan amount that the latex will coagulate far below the boiling point ofwater, for instance at a temperature in the range of 35° C. to 95° C.,or from about 35° C. to 65° C.

Without wishing to be bound by theory, it is believed that a drying stepafter application of the triggerable binder solution and beforeapplication of the wetting composition enhances bonding of a fibroussubstrate by driving the binder to fiber crossover points as moisture isdriven off, thus promoting efficient use of the binder. However, in analternative method, the drying step listed above is skipped, and thetriggerable polymer composition is applied to the substrate followed byapplication of the wetting composition without significant intermediatedrying. In one version of this method, the triggerable polymercomposition selectively adheres to the fibers, permitting excess waterto be removed in an optional pressing step without a significant loss ofthe binder from the substrate. In another version, no significant waterremoval occurs prior to application of the wetting composition. In yetanother alternative method, the triggerable polymer composition and thewetting composition are applied simultaneously, optionally withsubsequent addition of salt or other insolubilizing compounds to furtherrender the binder insoluble.

The present invention is further illustrated by the following examples,which are not to be construed in any way as imposing limitations uponthe scope thereof. On the contrary, it is to be clearly understood thatresort may be had to various other embodiments, modifications, andequivalents thereof which, after reading the description herein, maysuggest themselves to those skilled in the art without departing fromthe spirit of the present invention and/or the scope of the appendedclaims.

As used herein, the “thickness” of a web is measured with a 3-in acrylicplastic disk connected to the spindle of a Mitutoyo Digimatic Indicator(Mitutoyo Corporation, 31-19, Shiba 5-chome, Minato-ku, Tokyo 108,Japan) and which delivers a net load of 0.05 psi to the sample beingmeasured. The Mitutoyo Digimatic Indicator is zeroed when the disk restson a flat surface. When a sample having a size at least as great as theacrylic disk is placed under the disk, a thickness reading can beobtained from the digital readout of the indicator. Water-dispersiblesubstrates of the present invention can have any suitable thickness,such as from about 0.1 mm to 5 mm. For wet wipes, thicknesses can be inthe range of 0.2 mm to about 1 mm, more specifically from about 0.3 mmto about 0.7 mm. Thickness can be controlled, for example, by theapplication of compaction rolls during or after web formation, bypressing after binder or wetting composition has been applied, or bycontrolling the tension of winding when forming a roll good.

The use of the platen method to measure thickness gives an averagethickness at the macroscopic level. Local thickness may vary, especiallyif the product has been embossed or has otherwise been given athree-dimensional texture.

EXAMPLE 1

Polymers were synthesized by free radical polymerization of varyingcombinations of the following monomers: acrylic acid, acrylamide, butylacrylate, 2-ethylhexyl acrylate and [2(methacryloyloxy)ethyl] trimethylammonium chloride (“MQUAT”). Each polymerization was conducted inmethanol. A typical procedure is stated below.

Acrylamide (39.1 g, 0.55 mol), butyl acrylate (32.0 g, 0.25 mol),2-ethylhexyl acrylate (18.4 g, 0.10 mol), and MQUAT (27.6 g of 75 wt %solution, 0.10 mol) were dissolved in 50 g of methanol. A free radicalinitiator, 2,2″Azobisisobutyronitrile (“AIBN”) (0.66 g, 4.0×10′ mol) wasdissolved in 20 ml of methanol. The monomer solution was deoxygenated bybubbling N₂ through the solution for 20 minutes. To a 1000 ml roundbottom, three neck flask equipped with a condenser, two addition funnelsand a magnetic stirrer was added 125 g of methanol. The solvent washeated to gentle reflux under nitrogen. Monomers and initiator wereadded simultaneously from the addition funnels over a period of twohours. Polymerization was allowed to proceed for an additional twohours, at the end of which the addition funnels and condenser werereplaced with a distillation head and a mechanical stir rod to removemethanol. A steady stream of N₂ was maintained during distillation. Whenthe distillation was completed (about 3 hours), 400 g of deionized waterwas added to the polymer solution. The heat was removed and the solutionwas allowed to stir overnight.

Alternatively, the polymers can be made by adding the monomers andinitiator to the reaction flask all at once and reacting for four hours.This synthesis method is referred as “one pot” synthesis in thesubsequent section. A total of eight polymers were synthesized and theircompositions are summarized in Table 5 below.

TABLE 5 Polymer Composition Sample % MQUAT % AM % AA % BA % EHA 1 10 055  25 10 2 10 55  0 25 10 3 60 0 0 20 20 4 45 0 0 35 20 5 35 0 0 35 306 30 0 0 35 35 7 20 0 0 40 40 8 15 0 0 45 40

Sample Preparation

A water-dispersible, wet-laid nonwoven composed of BFF rayon fibers (1.5d×25 mm) was utilized as the base sheet for testing. Each base sheet wascut to an approximate size of 5.5 in (CD)×9 in (MD). A piece of releasepaper was placed onto a notepad, followed by a base sheet. Both pieceswere taped to the notepad with a single piece of Scotch tape. A #20grooved, wire-wound rod was laid across the top of the sample. A stripof the polymer solution to be tested was poured along the rod. The rodwas then rolled down the length of the sample, with gentle pressureapplied. Excess polymer was wiped off the bottom of the release paper,and the sample was placed into a forced air oven at 60° C. for at least10 minutes. The rod was cleaned between each sample as necessary. Oncethe samples were dry, they were removed from the oven. The top part ofeach sample was removed with a paper cutter. Each sample was then peeledfrom the release paper and the excess polymer film was gently pulledfrom the edges of the sample. Each sample sheet was then cut into ten 1in (CD)×4 in (MD) strips.

Tensile Testing

The SinTech 1/D tensile tester with Testworks 3.03 version software wasutilized for all sample testing. All testing was conducted in themachine direction using a 50 pound load cell and pneumatic, rubberizedgrips. The gage length was set at 3 in, and the crosshead speed was 12in/min. The wet samples were secured in the grips and stretched tofailure. The peak load of each sample was recorded as the data ofinterest. The data was not normalized to a 100% add-on level. A value of“0” was entered for the peak load if the sample was determined to bedispersed. Samples were considered dispersed if individual strips couldnot be removed from the salt solution intact due to lack of structuralintegrity.

The in-use strength of each sample was simulated by soaking the tensilesamples in various salt solutions. The concentrations of the saltsolutions were chosen based upon a 2 wt % NaCl solution, which isequivalent to 0.34 M. The 0.68 M and 1.36 M NaCl solutions correspond to4 wt % and 8 wt %, respectively. The same molarities were chosen foreach of the other salts tested, though the weight percents are notnecessarily equivalent to the sodium chloride solutions. Salt solutionstested included 0.34 M NaCl, 0.68 M NaCl, 1.36 M NaCl, 0.34 M CaCl₂,0.68 M CaCl₂, 1.36 M CaCl₂, 0.34 M Na₂SO₄, 0.68 M Na₂SO₄, 1.36 M Na₂SO₄,0.17 M ZnCl₂, 0.34 M ZnCl₂, 0.51 M ZnCl₂, 0.34 M ZnSO₄, 0.17 MZnCl₂+0.17 M NaCl, 0.34 M LiCl, 0.34 M KCl, 0.34 M Na₃PO₄, and 0.34MMgCl₂.

Twenty-four tensile samples were placed into the salt solution to betested and allowed to soak overnight. Strips were added to the saltsolution one at a time in order to avoid sticking the samples together.Average soaking time was approximately 17 hours, and volume of soakingsolution was held constant at approximately 500 mL. Following theovernight soak, eight samples were tested directly to determine the peakload. This test simulated storage and in-use strength. Eight sampleswere placed into 200 ppm Ca²⁺/Mg²⁺ for 1 hour, and eight samples wereplaced into 200 ppm Ca²⁺/Mg²⁺ for 3 hours. The peak load of the sampleswas measured following the soaking times. This test simulated disposalin the hardest water found in the United States.

Trigger Property

Polymer 1 showed salt sensitivity and significant strength in severalsolutions of sodium chloride. However, the polymer failed to disperse in200 ppm Ca²⁺/Mg²⁺, as shown in Table 6 below.

TABLE 6 Tensile strength of acrylic acid based polymer (g/in) SaltOvernight 1 hr. in 3 hr. in Concentration soak hard water hard water0.34 M 565 606 648 0.68 M 639 649 634 1.36 M 722 600 608

It is suspected that the positive charge on the polymer promotesdissociation of carboxylic acid groups creating carboxylate anions.Complex formation between the carboxylate anion and Ca²⁺ leads tocross-linking, which prevents dispersion in hard water. In order toobtain hard water dispersibility, the acrylic acid was replaced withacrylamide, a water-soluble monomer. The acrylamide polymer (sample 2)showed trigger behavior in several salt solutions as summarized in Table7 below.

TABLE 7 Tensile strength of acrylamide based polymer in various saltsolutions (g/in) Salt Overnight 1 hr. in 3 hr. in Solution Soak HardWater Hard Water 0.34 M NaCl 311 0 0 0.68 M NaCl 317 0 0 1.36 M NaCl 4290 0 0.34 M CaCl2 664 636 656 0.68 M CaCl2 635 662 666 1.36 M CaCl2 603616 596 0.34 M Na2SO4 289 0 0 0.68 M Na2SO4 486 160 0 1.36 M Na2SO4 897265 181 0.17 M ZnC12 345 0 0 0.34 M ZnZ12 519 0 0 1.36 M ZnC12 661 0 0

General trends showed that increasing the concentration of the saltsolution increased the in-use strength of the polymer binder. Theperformance of the polymer is salt-specific. The polymer showed moderatestrength and good dispersibility in NaCl. The strength of the polymerincreased almost linearly with increasing Na₂SO₄ concentration, butreached good strength only at higher salt level. The dispersibility wentin the opposite direction. The polymer showed nice strength in ZnCl₂ andgood dispersibility. For CaCl₂, the polymer showed good strength,independent of salt concentration in the range of investigation, but nostrength loss was observed when placed in hard water. Both resultssuggested the cross-linking of the polymer caused by Ca²⁺. Acrylamidehas been generally regarded as salt insensitive, and its interactionwith Ca²⁺ is unknown. Based on the fact that the polymer dispersed wellin hard water when soaked in other salts, such as ZnCl₂ and NaCl, it isclear that retardation only occurs above certain Ca²⁺ concentrations.

One concern with acrylamide based polymer is the toxicity of theresidual acrylamide monomer in the polymer solution. To avoid the safetyconcern, acrylamide was removed from the composition. Sample 3-8 weremade with only three monomers: MQUAT, BA and EHA. Table 8 summarizedtheir trigger behavior.

TABLE 8 Soluble properties of polymers of MQUAT, BA and EHA Sample 3 4 56 7 8 Solubility soluble soluble dispersed dispersed triggered insoluble

They differ greatly in the salt sensitivity as small changes incomposition can have large effects on the behavior of the polymer insolution. In general, their solubility decreases with decreasing MQUATcontent. Samples 3 and 4 were soluble in water even in very high saltconcentrations. Samples 5 and 6 were soluble in water and precipitatedat high salt level, but showed no strength. Sample 8 is insoluble inwater due to high hydrophobicity. Sample 7 had the best trigger propertyfor its delicate balance between the hydrophobic and hydrophilicmonomers. The behavior of the polymer in various salt solutions is shownin Table 9 below.

TABLE 9 Performance of polymer 7 in various salt solutions (g/in)Overnight Soak in 1 hr. Soak 3 hr. Soak Salt Solution Salt Solution inHard Water in Hard Water 0.34 M LiCl 65 0 0 0.34 M NaCl 66 0 0 0.34 MKCl 81 0 0 0.34 M MgCl₂ 96 0 0 0.34 M CaCl₂ 183 0 0 0.34 M ZnCl₂ 861 3325 0.17 M ZnCl₂ + 819 27 12 0.17 M NaCl 0.065 M ZnCl₂ + 370 0 0 0.15 MNaCl 0.34 M Na₂SO₄ 0 0 0 0.34 M Na₃PO₄ 895 736 699

The polymer displayed trigger property in monovalent salts, namely LiCl,NaCl and KCl, but it lacked any significant strength, falling far shortof the minimum goal of 300 g/in for in-use strength. The performance indivalent cations was highly selective. The polymer showed unremarkablestrength in MgCl₂ and CaCl₂, but displayed excellent strength of over800 g/in in ZnCl₂. The polymer also had excellent triggerability inmixed salt of 0.1 7M ZnCl₂ and 0.17 M NaCl. When the ZnCl₂ concentrationwas reduced to 0.065M, the strength was reduced. The polymer showed goodhard water dispersibility from all those salts.

The effect of anions, especially multivalent anions, on the triggerproperty was tested. The strength of the polymer in NaCl isunremarkable, though the dispersibility is good. The polymer possessedzero strength in Na₂SO₄. Following this discovery, the polymer was alsotested in ZnSO₄, in order to compare the exceptional strength of thepolymer in Zn²⁺ ion to its complete lack of strength in SO₄ ²⁻ ions. Thepolymer displayed zero strength in ZnSO₄ solution. The polymer forms anon-dispersible complex with phosphate ions, as it would not evendisperse after several hours in deionized water. Fortunately, phosphateion is extremely rare in waste water streams, and thus should pose noproblem for the dispersibility of the polymer once in a productapplication.

The “one pot” polymer, which contains 20% MQUAT, 40% BA and 40% EHA,displayed excellent strength of 896.6 g/in following the overnight soak.However, the dispersibility of the “one pot” polymer was not as good asthat of the model polymer, as it still displayed 138.7 g/in of strengthafter one hour in hard water, and 90.2 g/in of strength after a threehour soak. Overall, the “one pot” polymer displays good triggerproperty. Although the result using the “one pot” were below the desiredresults, it is believed that a “one pot” polymer having acceptablestrength properties can be made by optimization of the polymer designand is therefore considered within the scope of the present invention.

EXAMPLE 2

Polymerization

Polymers were synthesized by free radical polymerization in the samemanner as described above. MQUAT, n-butyl acrylate (BA), and2-ethylhexyl acrylate (EHA) were utilized in ratios indicated in Table10.

Polymer composition was characterized by ¹³C NMR and the compositionsfor each sample appear in Table 11. In most cases the polymercompositions agree with the feed ratios within a few percentage points.This would be expected for a homogeneous solution polymerization whereall the monomers have a similar reactivity.

TABLE 10 Polymer Feed Ratios mole % Feed mole % Feed mole % Feed SampleNB # MQUAT BA EHA #1 (028) 7421-028 20.0 40.0 40.0 #2 (041) 7421-04115.8 42.1 42.1 #3 (046) 7421-045 243 43.2 32.4 #4 (064) 7421-064 21.739.1 39.1 #5 (075) 7421-075 12.6 58.9 28.5 #6 (083) 7421-083 20.0 80.00.0 #7 (094) 7421-094 17.9 41.1 41.0 #8 (100) 7421-100 14.5 42.8 42.7 #9(130) 7421-130 27.3 30.4 36.3

TABLE 11 Polymer Composition mole % MQUAT mole % BA mole % EHA SampleFound Found Found #1 (028) 19.5 43.4 37.1 #2 (041) 18.1 46.4 35.5 #3(045) 25.7 43.3 31.0 #4 (064) 22.8 403 36.8 #5 (075) 12.1 59.4 28.5 #6(083) 20.2 79.8  0.0 #7 (094) 18.3 46.2 35.5 #8 (100) 13.3 47.6 39.1 #9(130) 25.6 40.5 33.9

Sample Preparation

Two base sheet materials were utilized to evaluate the cationic binders.The first was a water-dispersible, wet-laid non-woven composed of BFFrayon fibers (1.5 d×25 mm). Each base sheet was cut to an approximatesize of 5.5 in (CD)×9 in (MD). A piece of release paper was placed ontoa notepad, followed by a base sheet. Both pieces were taped to thenotepad with a single piece of Scotch tape. A #20 grooved, wire-woundrod was laid across the top of the sample. A strip of the polymersolution to be tested was poured along the rod. With gentle pressureapplied, the rod was then rolled down the length of the sample. Excesspolymer was wiped off the bottom of the release paper, and the samplewas placed into a forced air oven at 60° C. for at least 10 minutes. Therod was cleaned between each sample as necessary.

Once the samples were dry, they were removed from the oven. The top partof each sample was removed with a paper cutter. Each sample was thenpeeled from the release paper and the excess polymer fill was gentlypulled from the edges of the sample. Each sample sheet was then cut intoten 1 in (CD)×4 in (MD) strips. Add-on for these samples was in therange of 100%.

The second material used was an uncreped through-air dried (UCTAD)tissue basesheet made in the following fashion. A single ply, blended,uncreped through-air dried tissue basesheet was made generally inaccordance with U.S. Pat. No. 5,607,551 issued Mar. 4, 1997 toFarrington et al.(the disclosure of which is incorporated herein byreference). More specifically, 65 pounds (oven dry basis) of eucalyptushardwood Kraft fiber and 35 pounds (oven dried basis) of NorthernSoftwood Kraft (NSWK) fiber were dispersed in a pulper for 25 minutes ata consistency of 3% and refined before being transferred to a machinechest and diluted to a consistency of 1%. Prior to forming, the stockwas further diluted to approximately 0.1% consistency and transferred toa single layer headbox in such a manner as to provide a blended sheetcomprising 65% Eucalyptus and 35% NSWK. The formed web wasnon-compressively dewatered and rush transferred to a transfer fabrictraveling at a speed about 25 percent slower than the forming fabric.The web was then transferred to a through drying fabric and dried. Thetotal basis weight of the resulting sheet was 18.5 pounds per 2880 ft².

The binders were applied via spraying from a pressurized chamber anddried in a through-air drying oven at 165° C. for 2 min. Approximatebinder add-on was 20% for all UCTAD samples. Samples were then cut asnoted above.

Tensile Testing

The SinTech 1/D tensile tester with Testworks 3.03 version software wasutilized for all sample testing. The testing was conducted using the 60pound load cell and pneumatic, rubberized grips. The gage length was setat 2 in, and the crosshead speed was 12 in/min. The wet samples weresecured in the grips and stretched to failure. The peak load of eachsample was recorded as the data of interest. A value of “0” was enteredfor the peak load if the sample was determined to be dispersed. Sampleswere considered dispersed if individual strips could not be removed fromthe salt solution intact due to lack of structural integrity.

The in-use strength of each sample was simulated by soaking the tensilesamples in various salt solutions noted below. Disposal strength ordispersibility was assessed by transferring samples soaked for a minimumof 12 hours in the salt solutions into deionized water or a hard watersimulant (200 ppm Ca²⁺/Mg²⁺). NaCl (4%) was utilized as well as severaldivalent metal salts were employed. ZnCl₂ at various levels was employedas well as MgCl₂, CaCl₂, ZnSO₄, and MgSO₄. Unless otherwise noted, thetesting methods were the same as disclosed in Example 1.

Trigger Properties

Data demonstrating the trigger properties for the co- and terpolymers inthis study are shown in Tables 12 through 20. Tables 12 and 13 show thecross-deckle wet tensile (Peak Load in g/inch), CDWT, in concentratedNaCl and ZnCl₂ solutions. The order of the samples has been rearrangedto list them in order of increasing hydrophilicity.

TABLE 12 Wet Tensile Values (g/in.,) for NaCl Wetting Solutions (BFFRayon) Sample % MQUAT 5.2% NaCl 4% NaCl DI water Hard water #5 (075)12.1 826.5 494.3 572.2 #8 (100) 13.3 1238.6 844.6 908.0 #2 (041) 18.1241.1 158.7 114.5 #7 (094) 18.3 736.9 28.0 173.1 #1 (028) 19.5 174.314.4 12.1 #6 (083) 20.2 60.8 56.2 2.4 0.0 #4 (064) 22.8 28.2 41.1 0.91.9 #9 (130) 25.6 9.1 0.0 0.0 #3 (045) 25.1 7.4 0.0 0.0

The trigger behavior in NaCl indicates a relatively narrow range ofuseful compositions At level of 18% MQUAT and below, the binders showgood web strength, but fail to re-disperse in DI water or hard water. Atmoderate incorporation of the MQUAT monomer (˜19-22%), some useful webstrength is indicated in 4% NaCl. The rayon webs subsequently loosevirtually all of their strength in DI and hard water. At relatively highincorporation of MQUAT (>25%), the web strength is below target valuesin 4% NaCl. The optimum trigger composition appears to containapproximately 20% MQUAT. Note that Sample #6 is a 20/80 MQUAT/BAcopolymer, while Sample #1 has a roughly equivalent amounts of BA andEHA.

TABLE 13 Wet Tensile Values (g/in.) for 4% ZnCl₂ Wetting Solutions (BFFRayon) Sample % MQUAT 4% ZnCl₂ DI water Hard water #5 (075) 12.1 1019.2445.5 403.5 #8 (100) 13.3 1189.9 1180.2 658.1 #2 (041) 18.1 546.6 110.485.1 #7 (094) 18.3 1107.8 159.6 658.1 #1 (028) 19.5 743.3 26.5 29.2 #6(083) 20.2 679.1 4.2 0.3 #4 (064) 22.8 981.2 5.0 4.9 #9 (130) 25.6 726.79.2 8.9 #3 (045) 25.7 776.4 1.5 0.0

A much broader range of useful trigger compositions is evident forsamples in a 4% ZnCl₂ solution. Samples containing ˜19 to 26% MQUATexhibit very good web strength in the salt solution, but completelyloose strength when transferred to DI water or hard water. Binders withapproximately 18% or less MQUAT still fail to disperse when transferredto deionized water (DI) water or hard water. One explanation for thediffering behavior in NaCl and ZnCl₂ is ionic strength. The ionicstrength (I) value for 4% ZnCl₂ is 0.88, as opposed to an I value of0.68 for 4% NaCl. The divalent Zn²⁺ ion has a larger effect on ionicstrength, and, thus, the two values are not equivalent at identicalweight percent.

It can be demonstrated, however, that ionic strength effects alonecannot account for the difference in observed behavior. Table 12 showswet tensile values for Samples #4 and #6 in 5.2% NaCl (I=0.89), whichhas an almost identical I as 4% ZnCl₂. The binders still fail to developuseful strength properties even in 5.2% NaCl. In fact, the wet tensilevalues in 4% ZnCl₂ are still significantly higher.

To more systematically examine the effect of ZnCl₂ on the properties ofthe binders, a study using 4, 3, 2, and 1% of the salt was performed.These data appear in Tables 14-17 below. At 4% and 3% ZnCl₂, Samples 1,6, 4, 9, and 3 exhibit good trigger properties. Sample #7 exhibits goodweb strength, but fails to dispersed completely in DI and hard water.Samples 2, 8, and 5 are too hydrophobic to exhibit trigger properties.At 2% ZnCl₂, only Sample #1 exhibits good web strength anddispersibility. More hydrophilic samples fail to show sufficient webstrength, while more hydrophobic ones do not fully disperse.

TABLE 14 Repeat of Wet Tensile Values (g/in.) for 4% ZnCl₂ WettingSolutions (BFF Rayon). Sample 4% ZnCl₂ DI water Hard water #5 (075)658.2 252.5 255.2 #8 (100) 709.9 337.5 352.2 #2 (041) n/a n/a n/a #7(094) 675.1 50.9 70.4 #1 (028) 622.0 18.2 19.2 #6 (083) 561.6 3.3 2.4 #4(064) 512.4 8.1 15.9 #9 (130) 574.1 0.0 0.0 #3 (046) 590.2 5.5 8.8

TABLE 15 Wet Tensile Values (g/in.) for 3% ZnCl₂ Wetting Solutions (BFFRayon). Sample 3% ZnCl₂ DI water Hard water #5 (075) 729.1 268.4 281.5#8 (1100) 671.3 281.7 318.7 #2 (041) n/a n/a n/a #7 (094) 676.9 43.363.5 #1 (028) 535.0 6.9 13.4 #6 (083) 324.5 0.0 0.0 #4 (064) 516.0 4.610.4 #9 (130) 288.5 0.0 0.0 #3 (046) 497.4 2.1 7.8

In 1% ZnCl₂, Sample #1 indicates some trigger property, but the level ofstrength developed is below preferred levels. Interestingly, at this lowlevel of salt, Sample #7 exhibits some useful trigger properties. Thestrength is in the low range and the dispersibilty is slightly less thandesired, but the effect is clear.

TABLE 16 Wet Tensile Values (g/in.) for 2% ZnCl₂ Wetting Solutions (BFFRayon), Sample 2% ZnCl₂ DI water Hard water #5 (075) 615.9 177.9 253.3#8 (100) 651.6 322.9 347.6 #2 (041) n/a n/a n/a #7 (094) 552.0 34.5 71.5#1 (028) 385.8 6.0 8.9 #6 (083) 0.0 0.0 0.0 #4 (064) 89.9 0.0 4.5 #9(130) 0.0 0.0 0.0 #3 (045) 12.4 0.0 0.0

TABLE 17 Wet Tensile Values (g/in.) for 1% ZnCl₂ Wetting Solutions (BFFRayon). Sample 1% ZnCl₂ DI water Hard water #5 (075) 474.09 293.02279.90 #8 (100) 482.82 258.83 298.85 #2 (041) n/a n/a n/a #7 (094)200.91 9.36 24.90 #1 (028) 48.42 0.00 0.00 #6 (083) 0.00 0.00 0.00 #4(064) 0.00 0.00 0.00 #9 (130) 0.00 0.00 0.00 #3 (045) 0.00 0.00 0.00

It is apparent that the hydrophobic/hydrophilic balance is veryimportant with these cationic binders, even though the trigger range andlevel of salt necessary are much broader. To further demonstrate thiseffect, MQUAT polymers with 0, 50, and 20 mole % BA were synthesized andtested. These data appear in Table 9. The MQUAT homopolymer and the50/50 BA copolymer fail to show sufficient strength in the web. The20/80 MQUAT/BA copolymer exhibits good strength and dispersibility in 4%ZnCl₂. Clearly, the level of hydrophobe plays a role in the adhesiveproperties of these binders.

TABLE 18 Effect of BA Co-monomer on Wet Tensile (BFF Rayon). CDWT CDWTmole % mole % (g/in.) (g/in.) Feed Feed CDWT DI Hard Sample NB# MQUAT BA(g/in.)ZnCl₂ Water Watcr #10 6787-34 20 80 560.3 0 0 #12 6787-54 50 50 00 0 #11 6787-38 100 0 0 0 0

An UCTAD tissue substrate was also examined using ˜20% add-on of the20/80 MQUAT/BA copolymer (#6). CDWT as a function of percent ZnCl₂solution is shown in Table 19. In general, the same trends seen with therayon basesheets are apparent. However, the dispersibility for 4% and 3%ZnCl₂ seems to suffer on the UCTAD basesheet. At 2% ZnCl₂, the systemactually seems to show a good balance of strength and re-dispersibility.The strength falls below an acceptable level when 1% ZnCl₂ is employed.

TABLE 19 Effect of % ZnCl₂ on CDWT for UCTAD tissue using Sample #6 %ZnCl₂ Salt solution DI water Hard water 4 396.7 n/a 36.4 3 522.3 18.4 34 2 296.2 2.2 11.7 1  55.9 0.1 0.2

The effect of other divalent ions, as well as the effect of differentcounterions is shown in Table 20. Good strength is apparent in 4% ZnCl₂,as noted before. Also, other salts of divalent ions, such as MgCl₂ andCaCl₂ can provide trigger properties at acceptable strength levels.However, when the sulfate salts of these ions are employed, insufficientstrength or trigger properties result. Apparently, the trigger behaviorin these systems is mediated by both the cation and the anion of thesalt employed.

TABLE 20 Effect of divalent ions and counterions on CDWT using Sample #6on UCTAD tissue Salt Type 4% Solution DI water Hard water ZnCl₂ 364.237.6 49.4 MgCl₂ 133.9 6.6 8.6 CaCl₂ 93.3 3.9 7.4 ZnSO₄ 9.8 7.9 13.3MgSO₄ 15.6 8.8 15.4

These results seem to indicate “ion specific” interactions rather thanthe “salting-out” effect seen in previous systems. Although ionicstrength may play a role here, the data presented here clearly indicatesa new type of trigger mechanism based on hydrophobic associations andion-specific interactions.

EXAMPLE 3

Polymerization

Cationic triggerable polymers were synthesized by free radicalpolymerization in the same manner as described above. MQUAT, n-butylacrylate (BA), and 2-ethylhexyl acrylate (EHA) were utilized in thefollowing ratios: MQUAT 20 mole percent, BA 40 mole percent and EHA 40mole percent. It is stable in high salt solutions, such as 4 weightpercent ZnCl2, and is soluble in water when the salt concentration dropsbelow a certain level, such as 0.5 weight percent. Because of the natureof the charge groups the polymer carries, its dispersibility isvirtually unaffected by the presence of divalent cations, such as Ca²⁺and Mg²⁺ up to 200 ppm, and, therefore, the polymer performs well evenin the hardest water found in the United States households.

Wet Wipe Sample Preparation

To make a wet wipe product, the ion-sensitive cationic polymer wasapplied in an aqueous solution to a substrate by spraying. The substratewas a water-dispersible, wet-laid non-woven composed of BFF rayon fibers(1.5 d×25 mm). Two different binder solution were prepared. The firstsolution was an aqueous solution of the ion-sensitive polymer. The othersolution was an aqueous solution of the ion-sensitive polymer (75 weightpercent) and a co-binder (25 weight percent) in the form of an emulsionpolymer. The co-binder provides several advantages to the polymersystem, including rheology modification for better spray application,better binder penetration for higher strength, tack reduction and costsavings.

Selection of the emulsion system for the co-binder is critical. Theemulsion system of the co-binder must not interact with theion-sensitive cationic polymer such that it interferes with the triggerproperty. Three emulsion-based polymers were tested. Rovene 4817 astyrene butadiene copolymer manufactured by Mallard Creek Polymers,Charlotte, N.C., and Rhoplex P-376 a styrene acrylate copolymermanufactured by Rohm and Haas, Philadelphia, Pa. The combination of thecationic polymer and the Rovene 4817 and the Rhoplex P-376 caused severprecipitation of the binder from the aqueous solution. It was suspectedthat the anionic emulsion surfactants used in the Rovene 4817 and theRhoplex P-376 may have interacted with the cationically charged polymerthrough electrostatic forces, thus resulting in the precipitation of thebinder out of suspension. It was therefore determined that theseemulsion polymers were not suitable for use with the cationicion-sensitive polymer of the present invention.

The third emulsion polymer that was investigated was Duroset RB®manufactured by National Starch and Chemical Company. Duroset RB® is anethylene vinyl acetate copolymer. When the Duroset RB® was combined withthe cationic polymer, only a small amount of precipitation was observed,and did not interfere with the trigger property of the binder system.

Two different samples were prepared. One sample of the substrateincluded a binder made from only the cationic polymer; the othersubstrate contained a binder made from 75 weight percent cationicpolymer and 25 weight percent Duroset RB®. The samples were prepared inthe same manner as disclosed in co-pending U.S. patent application Ser.No. 09/564,939 assigned to Kimberly-Clark (the disclosure of which isincorporated herein by reference).

The samples were soaked in an aqueous solution containing 4 weightpercent ZnCl₂. The samples were then soaked in water containing 200 ppmCa²⁺/Mg²⁺. The samples were then tested for tensile strength. Theresults of this test are shown in Table 21 below.

TABLE 1 Trigger Performance of Cationic Binder 1 hr soak in 3 hr soak inSample 4% ZnCl₂ hard water hard water 100% Binder 861 33 25  75% Binder/714 11 0 25% Duroset RB  ®

The foregoing test results show that the tensile strength was reduced byabout 20% with the addition of 25% Duroset RB®. Both samples showedacceptable wet strength in the 4% ZnCl₂ solution. After one hour ofsoaking in 200 ppm Ca²⁺/Mg²⁺ solution, the peak load decreasedsignificantly. The strength was practically zero. After three hours ofsoaking, the sample containing the Duroset RB® was fully dispersedwithout shaking.

It is contemplated that emulsion polymers that use only a small amountof anionic surfactant or use a weak anionic surfactant may be used asthe co-binder in the present invention as long as they do not causeprecipitation to such an extent that it interferes with the triggerproperty of the polymer composition. It is also specificallycontemplated that other emulsion polymers using nonionic or cationicsurfactant systems may also be used as the co-binder in the presentinvention.

It should be understood, of course, that the foregoing relates only tocertain disclosed embodiments of the present invention and that numerousmodifications or alterations may be made therein without departing fromthe spirit and scope of the invention as set forth in the appendedclaims.

What is claimed is:
 1. A fibrous substrate comprising: fibrous material;a binder composition for binding said fibrous material into an integralweb, said binder composition comprising a cationic polymer comprisingcationic monomeric units and water insoluble, hydrophobic monomericunits; and a divalent metal salt capable of forming a complex anion inthe presence of said cationic polymer, whereby said fibrous substrate isinsoluble in aqueous solution containing at least about 0.5 weightpercent of said divalent metal salt and said fibrous substrate isdispersible in water containing up to about 200 ppm of one or more monoor multivalent ions.
 2. The fibrous substrate of claim 1, wherein saiddivalent metal salt is selected from the group consisting of ZnX₂, MgX₂,and CaX₂, wherein X is a halogen atom.
 3. The fibrous substrate of claim2, wherein said halogen atom is selected from the group consisting ofCl, Br and I.
 4. The fibrous substrate of claim 1, wherein said divalentmetal salt is selected from the group consisting of ZnCl₂, MgCl₂, andCaCl₂.
 5. The fibrous substrate of claim 1, where said cationicmonomeric units are selected from the group consisting of[2-(methacryloyloxy)-ethyl]trimethylammonium chloride,(3-acrylamidopropyl) trimethylammonium chloride,N,N-diallyldimethylammonium chloride, acryloxyethyltrimethylammoniumchloride, acryloxyethyldimethylbenzylammonium chloride,methacryloxyethyldimethylammonium chloride,methacryloxyethyldimethylbenzylammonium chloride and quaternized vinylpyridine.
 6. The fibrous substrate of claim 1, wherein said waterinsoluble hydrophobic monomeric units are selected from the groupconsisting of n-butyl acrylate and 2-ethylhexyl acrylate.
 7. The fibroussubstrate of claim 1, wherein said water insoluble hydrophobic monomericunits are selected from the group consisting of n-alkyl or branchedalkyl, substituted acrylamides, and acrylic esters.
 8. The fibroussubstrate of claim 1, wherein said water insoluble hydrophobic monomericunits are n-alkyl or branched alkyl substituted monomeric units.
 9. Thefibrous substrate of claim 1 further comprising hydrophilic orwater-soluble nonionic monomeric units.
 10. The fibrous substrate ofclaim 9, wherein said hydrophilic or water-soluble nonionic monomericunits are selected from the group consisting of acrylamide,methacrylamide, substituted acrylamides, substituted methacrylamides,hydroxyalkyl acrylates, hydroxyalkyl methacrylates, polyethyleneglycolacrylates, polyethyleneglycol methacrylates, and vinyl pyrrolidone. 11.The fibrous substrate of claim 1, wherein said cationic polymercomprises [2-(methacryloyloxy)ethyl] trimethyl ammonium chloride,n-butyl acrylate and 2-ethylhexyl acrylate and said divalent metal saltis selected from the group consisting of ZnCl₂, MgCl₂, and CaCl₂.
 12. Afibrous substrate comprising: fibrous material; a binder composition forbinding said fibrous material into an integral web, said bindercomposition comprising a cationic polymer comprising cationic monomericunits and water insoluble, hydrophobic monomeric units; a divalent metalion that is capable of forming a complex anion in the presence of saidcationic polymer; and an aqueous wetting solution, whereby said fibroussubstrate is insoluble in aqueous solution containing at least about 0.5weight percent of said divalent metal salt and said fibrous substrate isdispersible in water containing up to about 200 ppm of one or more monoor multivalent ions.
 13. A fibrous substrate comprising: fibrousmaterial; a binder composition for binding said fibrous material into anintegral web, said binder composition comprising a cationic polymercomprising cationic monomeric units and water insoluble, hydrophobicmonomeric units; and a divalent metal salt capable of forming a complexanion in the presence of said cationic polymer, whereby said fibroussubstrate is insoluble in aqueous solution containing at least about 0.5weight percent of said divalent metal salt and said fibrous substrate isdispersible in water containing up to about 200 ppm of one or more monoor multivalent ions.
 14. A fibrous substrate comprising: fibrousmaterial; a binder composition for binding said fibrous material into anintegral web, said binder composition comprising a cationic polymercomprising cationic monomeric units and water insoluble, hydrophobicmonomeric units; and at least about 0.5 weight percent of a divalentmetal salt, whereby said fibrous substrate is insoluble in aqueoussolution containing at least about 0.5 weight percent of said divalentmetal salt and said fibrous substrate is dispersible in water containingup to about 200 ppm of one or more mono or multivalent ions.